Concrete compositions with reduced drying time and methods of manufacturing same

ABSTRACT

Cementitious compositions and methods for preparing and using the cementitious compositions to yield hardened concrete. The cementitious compositions yield hardened concrete having reduced or attenuated water vapor emission and lower internal relative humidity (IRH). Cementitious compositions are characterized by the property of rapid surface drying while maintaining good workability, particularly when using porous lightweight aggregates that absorb substantial amounts of water. Methods of decreasing water availability and increasing surface drying of concrete, including lightweight concrete, are provided. A water soluble ionic salt may be used to sequester water within the pores and capillaries of the cement paste and/or porous lightweight aggreate by modifying the colligative propertie of pore water. The salt may be added directly to concrete or the concrete mix water, or, alternatively, aggregates may be infused with a water-salt solution to provide treated porous aggregates having improved water saturation and water retention.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation-in-part of PCT App. No.PCT/US2013/051356, filed Jul. 19, 2013, which claims the benefit ofearlier filed U.S. Provisional Application No. 61/673,927 filed Jul. 20,2012 and U.S. Provisional Application No. 61/709,428 filed Oct. 4, 2012,the disclosures of which are incorporated herein in their entirety.

BACKGROUND

1. Field of the Invention

The invention is in the field of concrete compositions, particularlyconcrete having decreased rate of water vapor emission, lower internalrelative humidity, and faster surface drying after hardening.

2. Related Technology

Concrete is a composite construction material composed primarily of thereaction products of hydraulic cement, aggregates, and water. Water isboth a reactant for the cement component and is necessary to providedesired flow characteristics (e.g., spread and/or slump) and ensureconsolidation of freshly mixed concrete to prevent formation ofstrength-reducing voids and other defects. Chemical admixtures may beadded to freshly mixed concrete to modify characteristics such asrheology (i.e., plastic viscosity and yield stress), water retention,and set time. Although some of the water reacts with the cementcomponent to form crystalline hydration products, a substantial portionremains unreacted and is typically gradually removed from concrete byevaporation. The continuing presence of water in concrete can poseproblems, particularly when applying a floor covering.

The discontinued use of volatile components in floor covering adhesivesfor concrete surfaces has created bonding and delamination problems.Concrete contains reaction water for cement hydration and water ofconvenience to facilitate workability and placement. Water is bothchemically bound and entrapped in gel and small capillaries comprisingabout 30-50% of the paste material, depending upon maturity. Water inconcrete must be consumed, sequestered, or evaporated into theatmosphere before a proper, permanent water-based adhesive bond can beassured. Unfortunately, the time necessary to accommodate the requisitedrying process is approximately one month per inch of concrete floordepth for standard weight concrete.

A cementitious composition for forming concrete generally refers to amixture of natural and/or artificial aggregates, such as, for example,sand and either gravel or crushed stone, which are held together bycement paste binder to form a highly durable building material. Cementpaste is typically made up of the reaction products of hydraulic cement,such as Portland cement, and water. Cement paste may also contain one ormore chemical admixtures as well as supplementary cementing materials,such as, for example, fly ash or ground granulated blast furnace slagcement (GGBFS).

Blended cements can comprise one or more pozzolan materials, which areprimarily glassy or non-crystalline siliceous or aluminosiliceousmaterials that are hydraulically reactive and have cementitiousproperties in the presence of excess calcium hydroxide provided byhydrating Portland cement. The silicates and aluminates of a pozzolanreacting with excess calcium hydroxide form secondary cementitiousphases (e.g., calcium silicate hydrates similar to those from Portlandcement, but possibly having a lower calcium to silicate ratio), whichprovide additional strengthening properties that usually begin afterabout 7 days of curing.

Blended hydraulic cement may comprise up to 40% or more fly ash, whichreduces the amount of water that must be blended with the cementitiouscomposition, allowing for improvement in later strength as the concretecures. Other examples of pozzolans that can be used in hydraulic cementblends include highly reactive pozzolans, such as silica fume andmetakaolin, which further increases the rate at which the concrete gainsstrength, resulting in a higher early strength. Current practice permitsup to 40% or more reduction in the amount of hydraulic cement used inthe concrete mix when replaced with a combination of pozzolans that donot significantly reduce the final compressive strength or otherperformance characteristics of the resulting concrete.

Lightweight aggregates are frequently designed into a concrete mix toreduce building dead load, enable longer spans, provide better seismicbenefits, increase fire resistance, and improve sound insulation. Thislightweight material commonly comprises expanded shale, clay, pumice,cinders, or polystyrene with a density of about ½ or less than that ofnormal aggregates and is capable of producing concrete that weighs from800 to 1000 pounds less per cubic yard.

In general, the weight reduction in lightweight aggregate is achieved bycreating a highly porous internal structure that can, unfortunately,also absorb up to 30% water. This water is in addition to the normalwater of convenience and can impart an additional amount to the concretemix equal to 2-3 times of that which must normally be consumed andevaporated, thereby further increasing the time-to-dry for adhesive orepoxy application. To prevent workability losses due to water absorptionduring mixing, transport and placement, porous aggregates are oftenpre-conditioned with water.

Should the concrete be conveyed to the location of placement by aconcrete pump, water absorption by the porous aggregates becomes morecritical, since the concrete may be subjected to liquid pressure withinthe pump and attendant line of up to 1000 psi (69 bar), which greatlycompresses the air in the pores and causes significant additional waterabsorption. Such pressure can force water required for workability intopreviously unsaturated pores of lightweight aggregates (i.e., poreswhich are not filled when subjected to atmospheric pressure but whichcan be filled at high pressures associated with pumping). Thus, completesaturation of the pores of lightweight aggregates is preferred toprevent workability loss and potential pump line obstructions underthese conditions.

Unfortunately, complete saturation is impractical since prolongedsoaking in water will not displace air trapped within the capillaries ofthe lightweight aggregate, so some loss of mix water during conveyancehas to be tolerated. Moreover, water instilled into porous aggregatesmay quickly evaporate in storage, returning the lightweight aggregatelargely to its previous dry condition within days. Thus, pre-wettedaggregates must be used almost immediately to capture the desiredbenefit.

Moreover, even these methods often do not typically result in fullysaturated capillaries. Any remaining empty capillaries, when subjectedto pump pressures, partially fill with water in response, compressingthe air trapped in the capillaries of the lightweight in accord with theUniversal Gas Law, thus resulting in the aforementioned workabilitylosses and potential line clogging during pumping. This can have severalconsequences: additional water must be added to the concrete mix priorto pumping to maintain workability sufficient to facilitate pumping.Thereafter, when the concrete exits the pump and returns to normalatmospheric pressure, the excess water responds to the compressed airwithin the lightweight aggregates and is partially forced back out intothe mix. This, in effect, increases the water-to-cement ratio,excessively diluting the plastic concrete mix and impacting the hardenedconcrete's permeability.

The cementitious materials in concrete require water, typically known aschemical water or hydration water, to chemically evolve into a hard,crystalline binder. For example, Portland cements generally require upto about 40% of their weight in water in order to promote completehydration and chemical reaction.

Excess water has conventionally been added to make concrete more plasticallowing it to flow into place. This excess water is known as water ofconvenience. A small amount of the water does escape as a result ofsolids settling during the plastic phase, evaporation at the atmosphericinterface, and absorption into accepting interface materials. However,much of the water of convenience remains in the concrete during andimmediately following hardening. The water of convenience can thenescape into the atmosphere following the hardening of the concrete. Thewater of convenience, depending on, among other things, the water tocementitious ratio, may represent up to about 70% of the total water inthe concrete.

The concrete construction and floor-covering industries may incur bothconstruction delays and remedial costs as a result of water vaporemissions and water intrusion from concrete. For example, adhesives andcoatings used in the construction of concrete floors are relativelyincompatible with moisture that develops at the concrete surface.Moisture may also create an environment for promoting the growth ofmold.

Water tightness in concrete structures is a measure of the ability ofthe hardened concrete to resist the passage of water. Water vaporemission is proportional to the state of relative dryness of the body ofthe concrete structure. Once isolated from external sources of water,water vapor emissions are derived from the amount of water that is usedin excess of that needed to harden the cementitious materials—i.e., thewater of convenience. Depending upon the atmospheric temperature andhumidity at the surface and the thickness of the concrete, theelimination of excess water through water vapor emissions can takemonths to reach a level that is compatible with the application of acoating or an adhesive.

There is also a possibility that water may develop under the floor dueto flooding, water backup, etc. Hardened concrete that resists watervapor permeation is capable of further protecting any coatings that havebeen applied to the surface of the concrete. There is a need in the artfor a concrete that, once it becomes hardened, is substantiallyresistant to water vapor permeation.

Installation of an impermeable barrier on the surface of the concreteprior to reaching an acceptable level of dryness may result in moistureaccumulation, adhesive failure, and a consequential failure of thebarrier due to delamination. Premature application of coatings andadhesives increases the risk of failure, while the delay caused bywaiting for the concrete to reach an acceptable level of dryness mayresult in potentially costly and unacceptable construction delays.

The floor covering industry has determined, depending on the type ofadhesive or coating used, that a maximum water vapor emission rate offrom 3 to 5 pounds of water vapor per 1,000 square feet per 24 hourperiod (lb/1000 ft²/24 h) is representative of a state of slab drynessnecessary before adhesive may be applied to the concrete floor.Accordingly, there remains a long-felt but unsatisfied need in the artfor cementitious compositions that reduce the amount of time needed toreach a desired water vapor emission rate in concrete floors enabling amore timely application of coatings and adhesives.

It is known in the art that certain polymers classified assuperplasticizers may be included in concrete in order to reduce theamount of water of convenience needed to allow the cementitious mix tomore readily flow into place. Certainly, a reduction in the amount ofexcess water remaining after the concrete hardens should lead to areduction in the amount of time necessary to reach a desired water vaporemissions rate. However, the use of superplasticizers alone does notaddress other effects that influence the rate of water vapor emissionfrom the concrete.

Accordingly, there remains a need in the art for cementitiouscompositions that further reduce the amount of time necessary to reach adesired water vapor emission rate in concrete floors beyond that whichis achieved through a reduction in the amount of water required throughthe use of a superplasticizer additive.

If attainment of faster drying lightweight concrete is an objective, theusual method of water reduction by utilizing large doses ofsuperplasticizers (very high range water reducers) is difficult becauseof the sensitivity of the mix to the loss of the enhanced efficiencywater (Field workability consistency). Furthermore, high doses ofsuperplasticizers tend to impart a thixotropic characteristic exhibitedby workability loss if deprived of mixing shear. This loss of mixingshear often occurs during pump hose movement or delay in concretesupply. Because the efficiency of admixture-treated water is improved,loss of water by temporary absorption into the pores of lightweightaggregates during pressurized pumping has both a substantially greaternegative impact on workability and a greater negative impact causingpotential segregation and bleeding when the admixture-treated water isreleased from the pores of the aggregates after exiting the pump.

Similarly, the inclusion of silica fume or metakaolin both well-known.Highly reactive pozzolans possess very high surface areas and thereforeagain require super-plasticizer to reduce water and maintainworkability. It also has been found that highly super-plasticizedconcrete is more difficult to air entrain. Air entrainment is animportant feature of lightweight concrete, since it aids in reducingweight and lowers the mortar density thereby attenuating the tendency ofthe coarse lightweight aggregate particles to float to the surface andhinder finishing operations.

The absorbed water and resulting added mixture water caused by pumpingconcrete containing porous lightweight aggregates therefore posesdifficulties when accelerated drying of the concrete is desired. As aconsequence of concrete hydration and lowering of internal vaporpressure in the mortar, the additional water released from thecapillaries of the porous aggregates permeates the mortar in theconcrete. While this can be beneficial from the standpoint of promotingmore complete hydration of the cementitious binder, particularly inlower water-to-cement ratio systems, it can create a prolonged period ofrelatively high humidity within the concrete, resulting in moistconcrete that must dry out before it can be coated or sealed. Suchdrying is further retarded in humid climates.

The state of dryness within concrete is usually determined by drillingholes to accommodate in situ humidity probes. When these probes areinstalled at the depth required by ASTM F-2170-09, it is presumed to berepresentative of the future sealed equilibrium moisture condition ofthe full concrete thickness. Attainment of 75-80% relative humidity(some floor coverings tolerances may be slightly more or less) ensuresthat the concrete surface is ready for adhesive application. Experiencein the floor covering industry has validated research data whichindicates that if internal humidity probes are inserted to a depth of40% of a concrete structure having one side exposed to the atmosphere(20% if two sides are exposed) in accordance with ASTM F-2170-09,“Standard Method for Determining Humidity in Concrete Floor Slabs Usingin situ Probes”, and the probes indicate an internal relative humidityof 75-80%, that this is representative of the sealed future equilibriummoisture condition of the full thickness. If the internal relativehumidity is higher than 75-80%, it is assumed the floor will not acceptwater based glue and will generate sufficient vapor pressure todelaminate impervious coatings. Below that amount, and absent outsidemoisture influences, it is assumed the structure can accept water basedglue and not generate sufficient vapor pressure differential to de-bondimpervious coatings. Epoxy sealers are also sensitive to water vaporpressure and consequently, encounter similar problems. Prematureapplication of either water-soluble adhesive or epoxy sealer tounder-dried concrete can result in moisture accumulation beneath theapplied impervious surface and a potential for loss of bond with theepoxy or flooring. There are sealers that can be applied to attenuatethe water vapor emission, but they often fail, resulting in loss ofspace utilization during repair and occasionally creating costlylitigation. To reduce the risk of such problems, floors with excessivehumidity may require drying times of up to a year or more.

The substitution of the porous lightweight aggregates which absorb waterinstead of normal aggregates can prolong drying times by months or ayear or more. Research has demonstrated that high performance standardweight coarse aggregates concrete (HPC) can dry to satisfactory IRHcondition comparatively rapidly. These concretes have awater-to-cementitious ratio (w/cm) generally below 0.40 and can containfairly large amounts of cement or cement/pozzolans to achieve aninternal relative humidity of 75-80% as determined by ASTM F 2170. Anexample of the large water difference is shown in Table 1 below.

TABLE 1 dry, lbs dry, lbs High Light- dry, lbs Performance weight NormalConcrete (HPC) HPC Cement 300 400 400 GGBFS 200 400 400 Sand 1340 12741220 Stone 1750 1750 Lightweight 850 Water 325 285 325 plasticizer 10 oz40 oz. 40 oz. W/C 0.65 0.36 0.41 PCF 145 150.5 118.3 AE 1.30% 1.30% 5%Total W/C 0.70 0.39 0.60 Aggregate Water 23 23 151

Other research by Suprenant and Malisch (1998) reported that a 4 inchconcrete slab made from conventional concrete required 46 days to reacha moisture vapor emission rate (MVER) of 3.0 lb/1000 ft²/24 h. In 1990they reported that a lightweight concrete slab made with the same w/cmand cured in the same manner took 183 days to reach the same MVER, afour-fold increase.

The construction industry, therefore, faces a dichotomy. It can addresswater absorption by the porous aggregate with as much water as needed toensure pumpability and avoid critical workability loss in the pump lineand deal with the consequent prolonged drying time of up to a year oraccept the risk of floor failure by using a sealer to isolate themoisture-laden floor from an applied impervious coating or water solubleglue. The concrete construction and floor-covering industries maytherefore incur construction delays and/or remedial costs as a result ofwater vapor emissions and water intrusion from concrete. Moisture mayalso create an environment for promoting growth of mold.

BRIEF SUMMARY

Disclosed herein are concrete compositions that achieve faster surfacedrying compared to conventional concrete of similar or even lowerwater-to-cementitious binder ratio (w/cm). Also disclosed arecementitious compositions and methods for manufacturing hardenedconcrete having decreased internal relative humidity and rate of watervapor emission, which yield concrete having a faster drying outersurface. Concrete having accelerated surface drying characteristics anddecreased internal relative humidity can be advantageous for differentreasons, including sooner application of coatings and adhesives to thefaster-drying concrete surface compared to conventional concrete ofsimilar or lower w/cm.

In contrast to conventional methods for obtaining concrete with fastsurface-drying characteristics, which include lowering the w/cm of theconcrete and/or accelerating hydration of the cementitious binder, thecompositions and methods disclosed herein at least partially rely on theuse of one or more water-soluble salts to adjust the colligativeproperties of the remaining pore water in concrete. In this way,concrete of virtually any w/cm can be modified to have acceleratedsurface and internal drying characteristics. Whereas the amount of porewater remaining in hardened concrete at any given time is related to thew/cm and also the rate at which water is consumed by the hydrationreactions between water and cementitious binder(s), the colligativeproperties of the pore water can be controlled independently of the w/cmand hydration rate by including an appropriate quantity of dissolvedions within the pore water.

According to some embodiments, the colligative properties of the porewater in concrete is controlled by including one or more water solublesalts, such as one or more alkali metal salts, within the cementitiouscomposition or mix used to manufacture the concrete. The ions releasedfrom the water soluble salt(s) sequester unreacted pore water in thehardened concrete, which reduces the partial pressure of water vapor andthe internal relative humidity (IRH) within the hardened concrete.Reducing the partial pressure of water vapor and IRH in hardenedconcrete in turn reduces the rate of water vapor emission from thehardened concrete, which results in faster drying of the concretesurface. This advantageously permits sooner application of coatings,adhesives, or layers onto the concrete surface as compared to concreteof similar or even lower w/cm known in the art.

Based on the principles disclosed herein, the selection of anappropriate quantity of added ionic salt to achieve an IRH of 75-80% orbelow within a predetermined period of time can be determined forconcrete of virtually any w/cm and which hydrates at any known orpredicted rate. For example, a cementitious mixture can be designed toinclude an amount of hydraulic cement, water, and one or more ionicsalts so that water that has not reacted with hydraulic cement at apredetermined time period, such as within 50 days, 45 days, 40 days, 35days, 30 days, 28 days, 25 days, 20 days, 15 days, or 10 days, willcontain a sufficient concentration of ions so as to achieve an IRH of75-80% within the predetermined time period.

According to some embodiments, a cementitious mix can be designed withan amount of cementitious binder, water, and salt so that the moles ofremaining pore water, divided by the sum of remaining moles of freewater and available moles of dissolved ions, equals 0.75-0.80 or less,which is closely related to the partial pressure of water vapor as wellas the IRH within hardened concrete as determined by ASTM F-2170. Theaddition of non-volatile and substantially non-reactive (relative tohydraulic cement) salt to the water solution will decrease the IRH andtherefore the water vapor emission according to the number of soluteparticles present. According to some embodiments, there can be enoughsalt and cementitious material to ensure this eventual ratio within aspecified time period or range. However, if the added salt reacts withthe hydraulic cement binder, the concentration of ions within the freepore water contributed by the added salt will be substantially reducedover time by the degree of such reaction, which can add uncertainty andunpredictability to the system.

According to some embodiments, the relationship between the moles ofremaining free water and moles of dissolved ions required to achieve adesired IRH for hardened concrete of 75-80% or less within a specifiedtime period or range can be expressed according to Equation (I):

Moles Free Water÷(Moles Free Water+Moles Dissolved Ions)≦0.75-0.80  Equation (I).

As the dissolved ion concentration increases, the ratio according toEquation (I) also decreases, as do the partial pressure of water vaporand the IRH of hardened concrete. By understanding this relationship,one of ordinary skill in the art can estimate an appropriate quantity ofone or more salts that will yield hardened concrete that will have apredictable IRH of 75-80% or below within a predetermine time period orrange. In this way, one can quickly target a given salt and verify thisquantity by testing above and below the target to avoid adding eithertoo little salt, which could yield hardened concrete having a surfacethat dries too slowly, or too much salt, which can cause other problems,such as reduced strength and/or durability. Another important aspect ofEquation (I) is that as the amount of free water dissipates, either byevaporation of water from the concrete surface, continued cementhydration, or both, the numerator decreases at a faster rate than thedenominator because the moles of salt ions present remain unchanged.This further accelerates the rate at which desired surface humidity ofthe hardened concrete is attained as compared to the rate of surfacedrying of concrete and attainment of said surface humidity at the sameor even lower w/cm made in the absence or inadequate quantity ofdissolved ions.

Another important aspect of Equation (I) is that it is useful indetermining the appropriate quantity (e.g., weight) of binary salts tobe added to a cementitious or concrete composition that will yield thedesired ratio independently of molecular weight and/or the number ofions contributed by a particular salt compound. It is also useful indetermining an appropriate salt concentration independently of aggregatespecific gravity, such as when a lightweight aggregate is use. In fact,when using a porous lightweight aggregate that reduces the weight of acubic yard of concrete but increases the total amount of water and w/cmrequire to provide a desired flow, the weight percent of salt within thecementitious or concrete composition will typically be substantiallygreater than when using a normal aggregate. By relating the amount offree water, dissolved ions, and expected IRH within a predetermined timeperiod or range, Equation (I) normalizes for such differences inaggregate specific gravity, free water content, w/cm, and the molecularweight of salt.

In some embodiments, examples of water soluble salts that are effectivein increasing the colligative properties of the remaining pore waterinclude water soluble acetates, formates, sulfates, thiosulfates,nitrates, nitrites, bromides, chlorides, and thiocyanates of one or morealkali metals. For example, soluble alkali metal salts may be selectedfrom salts of lithium, potassium, sodium, and mixtures thereof.

Useful water soluble salts can have minimal reactivity with thehydraulic cement component and using Equation (I) can provide desiredand predictable colligative property information. Salts that react withhydraulic cement and are at least partially consumed during cementhydration are less able to increase the colligative property of waterbecause at least some of the ions contributed by such salts are consumedand therefore unavailable or produce other ions when determining theratio according to Equation (I). For example, it has been found thatsalts of alkaline earth metals are far less effective than salts ofalkali metals in reducing IRH and the rate of water vapor emission andincreasing the rate of surface drying of hardened concrete. It ispostulated that alkaline earth metal ions, such as calcium andmagnesium, react with silicate and aluminate ions and are taken out ofsolution. As a result, these ions are largely unavailable for increasingthe colligative properties of water.

In addition to the foregoing, because lowering the w/cm typically lowersthe amount of remaining pore water following the consumption of water ofhydration, it may be advantageous to include a water reducer, such as asuperplasticizer, also referred to as a high range water reducer (HRWR).Water reducers can be used to provide desired flow using less water,which permits concrete of desired slump at lower w/cm. In someembodiments, the superplasticizer can have a concentration in a rangefrom about 1 to about 6 ounces per 100 pounds of the hydraulic cement.

In some embodiments, the aggregate may comprise a porous aggregate thatis able to absorb and contain water. In such cases, the amount of saltcan be adjusted to account for the amount of absorbed water. Inaddition, the water soluble salt may reduce inflow and outflow of liquidwater from pores and capillaries of the porous aggregate in comparisonto concrete substantially free of the at least one water soluble salt,which can further reduce the water vapor emission rate from concrete.

Another aspect of the invention includes a method of manufacturing ahardened concrete comprising preparing a fresh concrete mixture byblending together an aggregate, one or more water soluble salts,hydraulic cement and water, the water including both water of hydrationand water of convenience, and allowing the water of hydration to reactwith the hydraulic cement to form hydrated cement paste having pores andcapillaries. The one or more water soluble salts enhance the retentionof free water by pores and capillaries of cement paste and inhibitdiffusion of water and/or water vapor to the surface of the hardenedconcrete. This, in turn, causes or allows the hardened concrete to morequickly achieve a desired internal humidity and surface dryness comparedto concrete made in the absence of the one or more salts.

In some embodiments, the water soluble salt permits the concrete toachieve 75-80% internal relative humidity, measured in accordance withASTM F 2170, with less total emission of water vapor from the concretecompared to a concrete substantially free of the water soluble salt. Inother embodiments of the invention, the at least one water soluble saltprovides cement paste having reduced autogenous and/or drying shrinkageof hardened concrete compared to concrete substantially free of thewater soluble salt.

According to some embodiments, the at least one water soluble salt isadded to the fresh concrete mixture upon blending together theaggregate, at least one water soluble salt, hydraulic cement, and water.In certain embodiments of the invention, at least a portion of the watersoluble salt can be indirectly added to the fresh concrete mixture byinfusing a porous lightweight aggregate with an aqueous solution of thesalt prior to blending together the aggregate, at least one watersoluble salt, hydraulic cement, and water. In some embodiments, thewater soluble salt has a concentration in the aqueous solution used toinfuse a porous aggregate of from about 2.5% to about 20% by weightbased on a total weight of the aqueous composition.

In some embodiments, infusing a porous lightweight aggregate with anaqueous salt solution improves workability of the fresh concrete mixturecompared to a concrete made in the absence of infusing the porouslightweight aggregate with the aqueous salt solution. In someembodiments, infusing the porous lightweight aggregate with the aqueoussalt solution improves pumpability and decreases workability loss whenpumping the fresh concrete mixture under pressure compared to concretemade in the absence of infusing the porous lightweight aggregate withthe aqueous salt solution.

These embodiments of the invention and other aspects and embodiments ofthe invention will become apparent upon review of the followingdescription taken in conjunction with the accompanying drawings. Theinvention, though, is pointed out with particularity by the appendedclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a chart illustrating the percentage of water loss of porouslightweight aggregates treated by tap water (Sample 43) and solutions ofseven different salts (Samples 44-50) after drying for 27 hours;

FIG. 2 is a chart illustrating unfilled pore space of porous lightweightaggregates treated by tap water (Sample 43) and solutions of sevendifferent salts (Samples 44-50) after drying for 27 hours and then beingre-immersed for 30 minutes, as indicated by weight percent of waterneeded to fully saturate the unfilled space of the aggregates;

FIG. 3 is a chart illustrating water vapor emission of concrete madefrom aggregates treated by tap water (Sample 51) and four solutions ofdifferent salts (Samples 52-55);

FIG. 4 is a chart illustrating water vapor emission of concrete madefrom aggregates treated by tap water (Sample 56) and four solutions(Samples 57-60), wherein aggregates were soaked in water (Sample 56) orboiled in aqueous solutions (Samples 57, 58, and 59) or partially driedthen dipped in an aqueous solution of 15% 20 NaAc and 5% NaC1 (Sample60);

FIG. 5 is a chart illustrating the close correlation between waterevaporation rate of lightweight concrete and the number of days requiredfor the concrete to reach 75% relative humidity, as measured by animmersion probe;

FIG. 6 is a chart illustrating the number of days required forlightweight concrete containing various salts to reach 75% relativehumidity, as measured by an immersion probe;

FIG. 7 is a chart illustrating the number of days required for normalweight concrete containing various salts to reach 75% relative humidity;

FIG. 8 is a graphical representation showing the relative humidity overtime for two exemplary embodiments of cementitious mixes of theinvention;

FIG. 9 is a chart illustrating the relative humidity over time forcementitious compositions having various concentration of sodium nitriteaccording to an embodiment of the invention;

FIG. 10 is a chart illustrating the relative humidity over time forcementitious compositions having various concentrations of sodiumnitrite according to another embodiment of the invention;

FIG. 11 is a graphical representation showing the relative humidity overtime for cementitious compositions having various concentrations ofsodium nitrite according to another embodiment of the invention;

FIG. 12 is a bar graph comparing 19-day internal relative humidityvalues of Test Runs 1 to 3;

FIG. 13 is a line graph comparing the internal relative humidity valuesof Test Runs 1 to 3 for all sampled days;

FIG. 14 is a bar graph comparing 19-day internal relative humidityvalues of Test Runs 4 to 7;

FIG. 15 is a line graph comparing the internal relative humidity valuesTest Runs 4 to 7 for all sampled days;

FIG. 16 is a bar graph comparing 10-day internal relative humidityvalues for Test Runs 1 to 7;

FIG. 17 is a line graph comparing the internal relative humidity valuesfor hardened concrete using different additives for Test Runs 8 to 13;

FIG. 18 is a line graph comparing the internal relative humidity valuesfor hardened concrete in Test Runs 14 to 16 using, no additive, sodiumformate, or calcium formate; and

FIG. 19 is a line graph of an exemplary concrete showing the degree ofhydration of the cement binder and compressive strength gain as afunction of time.

DETAILED DESCRIPTION Introduction

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Preferred embodiments of theinvention may be described, but this invention may, however, be embodiedin many different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Theembodiments of the invention are not to be interpreted in any way aslimiting the various inventions described herein.

Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation. Allterms, including technical and scientific terms, as used herein, havethe same meaning as commonly understood by one of ordinary skill in theart to which this invention belongs unless a term has been otherwisedefined. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningas commonly understood by a person having ordinary skill in the art towhich this invention belongs. It will be further understood that terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and the present disclosure. Suchcommonly used terms will not be interpreted in an idealized or overlyformal sense unless the disclosure herein expressly so definesotherwise.

By way of background, the colligative property of water in hardenedconcrete correlates with the total concentration of ions within thewater, including the concentration of ions provided by dissolovedhydraulic cement minerals, such as calcium, silicate, and aluminateions, and also the concentration of ions provided by the one or moreadded ionic salts. In the early stages of cement hydration and concretehardening, e.g., within a few hours or days of mixing, the water inconcrete can have high concentrations of calcium, silicate, andaluminate ions from the hydraulic cement. As cement hydration proceedsforward, however, these ions precipitate out and form cement hydrationproducts, such as calcium silicate hydrates (CSH) and calcium silicatealuminates (CSA), while consuming only a portion of the available water.

It has now been discovered that, in the absence of an additional sourceof ions, such as the one or more ionic salts added in accordance withthe invention, the colligative property of water in concreteprogressively decreases as the hydration reaction progresses. Therefore,water evaporation from the concrete surface becomes the only effectivemechanism for the IRH and water vapor emission rate to decrease inconcretes without additional ionic salt sources. This can take asignificant amount of time before the concrete surface driessufficiently to permit the application of coatings and adhesives. Inhumid climates this is particularly problematic as the rate of waterevaporation from concrete is slowed down by high ambient relativehumidity. The solution to this problem for concrete having any givenw/cm and degree of hydration within a predetermined time period (e.g.,within 50 days or less) is to include an amount of ions in order for theremaining water at the predetermined time period to have colligativeproperties so as to sequester water and achieve an internal relativehumidity (IRH) at or below a predetermined level (e.g., 75-80%) withinthe predetermined time period (e.g., within 50 days or less).

As discussed above, part of the water used to make freshly mixedconcrete is water of hydration, which is consumed over time in thehydration reaction with hydraulic cement to produce strength. Anotherpart of the water is water of convenience and is in excess of the waterof hydration. The hydration reaction that causes concrete to harden anddevelop strength proceeds over time, with portions of the water beingconsumed in hours, days, weeks, and months (See FIG. 19). Therefore, atany given time, the total amount of water available for evaporation froma concrete surface generally correlates with the sum of the water ofconvenience and the water of hydration that has not yet been consumed byhydraulic cement.

It has been discovered that the internal relative humidity (IRH) ofconcrete at any given time after placement and hardening generallycorrelates with two variables: (1) the amount of water remaining in theconcrete that has not reacted with hydraulic cement; and (2) itscolligative property, which is related to the concentration of ions(particles) within the remaining water. Increasing the concentration ofions in concrete pore water reduces the partial pressure of water vaporin concrete. In view of this, cementitious compositions, includingfreshly mixed concrete and other cementitious mixes, can be formulatedso as to include amounts of water, hydraulic cement, and one or moreadded ionic salts that yield hardened concrete which can achieve an IRHof 80% or less within a desired time period, such as within 50 days orless.

Based on the principles disclosed herein, the selection of anappropriate quantity of added ionic salt to achieve an IRH at or below80% within a predetermined period of time can be determined for concreteof virtually any w/cm and which hydrates at any known or predicted rate.For example, a cementitious mixture can be designed to include an amountof hydraulic cement, water, and one or more ionic salts so that waterthat has not reacted with hydraulic cement at a predetermined timeperiod, such as within 50 days, 45 days, 40 days, 35 days, 30 days, 28days, 25 days, 20 days, or 15 days, will contain a sufficientconcentration of ions so as to achieve an IRH of 75-80% within thepredetermined time period.

Because different salts can have greatly varying molecular weights, thenumber of ions provided per unit weight will vary with differingconcentrations, ion mixture and van der Waal's forces. Thus, the weightof the salt is less important than the quantity of water soluble ionsthat it contributes to the remaining pore water. Thus, salts with ahigher molecular weight will typically be added in greater weightamounts to provide the desired number of ions compared to salts withsmaller molecular weights. In addition, the appropriate number of ionsprovided by the salt to yield a desired IRH and water vapor attenuationis correlated with the amount of remaining water in the concrete at thepreselected time period. Concrete and cement pastes having a higher w/cmwill typically require more salt to achieve a desired colligativeproperty to control IRH, while cement pastes with lower w/cm willrequire less salt, all things being equal. Nevertheless, the appropriateamount of any salt of any given molecular weight, when used in concreteor cement paste of any given w/cm, can be determined using Equation (I)or similar equation once it has been determined how much pore water willremain in the hardened concrete at the preselected time period. In somecases, an excess of ions can be included to provide a margin of safety.On the other hand, it may be desirable to avoid including a large excessof ions, particularly to the extent that they may reduce long-termconcrete durability and/or substantially alter the rate of cementhydration.

Definitions

As used in the specification and in the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contextclearly indicates otherwise. For example, reference to “a concrete”includes a plurality of such concrete.

Exemplary compositions of the invention are described in the examplespresented herein. As a person having ordinary skill in the art to whichthis invention belongs would appreciate, variations or modificationsfrom these exemplary compositions, as detailed in the specification andas further set forth in the claims that follow, are intended to beincluded within the scope of the present invention.

As used herein, “wt %” or “weight percent” or “% by weight” or “percentby weight” and any variations thereof, unless specifically stated to thecontrary, means a weight percentage of the component based on the totalweight of the composition or article in which the component is included.“Wt %” or “weight percent” or “% by weight” or “percent by weight” andany variations thereof, when referring to a cementitious mix, means aweight percentage of the component based on the total weight of thecementitious compounds in the cementitious mix or the weight of thecementitious mix on a water-free basis.

The terms “attenuated water vapor emission” or “decreasing the rate ofwater vapor emission,” as may be used interchangeably herein, as well asany variation thereof, means a cementitious composition that ultimatelyprovides a cementitious mix that produces a hardened concretedemonstrating a reduction in the amount of time needed to achieve adesired water vapor emissions rate. In an embodiment of the invention,the desired water vapor emissions rate, for example, is 3 lb/1000 ft²/24h. In certain embodiments of the invention, the attenuated water vaporemission may be measured based on the number of days required to achievea desired internal relative humidity (IRH), for example, 75-80% IRH.

The term “concrete structure,” as used herein, is intended to be broadlydefined to refer to any structure that is composed, in at leastsignificant part, of a concrete which has cured and hardened. A concretestructure includes, but is not limited to, a bridge, a roadway, aparking lot, a sidewalk, a curb, a parking garage, a floor, a patioslab, a support column, a pier, a marine structure, a piling, a conduitand any other paved surface whether located inside or outside.

As used herein, a “cement replacement” is a compound that partiallysubstitutes for a compound that functions as the primary cementcompound, such as, for example, a hydraulic cement, in a cementitiouscomposition. Without intending to be bound by theory, the cementreplacement itself may have binding properties similar to a cement. Assuch, any compound that can be chemically reacted or hydrolyzed by waterto ultimately form other compounds that promote the hardening of acement may, in certain embodiments, be a cement replacement. In someembodiments of the invention, the cement replacement may demonstratecementitious properties because of their mere presence with anothercomponent of cement in the cementitious composition. A pozzolan is anon-limiting example of cement replacement that demonstratescementitious properties when in the presence of another component ofcement in the cementitious composition.

In certain embodiments of the invention, a cement replacement may bechosen to impart additional properties to the cement. In a non-limitingexample, calcium carbonate may not only function as a cementreplacement, but may also act as any one of a filler, a densifier, anaccelerator of hydration, and any combination thereof. The compositionsof the invention, in certain embodiments, may include these types ofcompounds as well. The terms “cementitious composition” or “cementitiousmix” or “concrete composition or “concrete mixture,” as may be usedinterchangeably herein, refer to the final mixture that comprises thecompounds intended to be part of the formulation used to pour or cast aconcrete. Such compositions or mixes or mixtures may refer to acomposition that includes a cement material and, optionally, any of apozzolan, one or more fillers, adjuvants, additives, dispersants, andother aggregates and/or materials that, typically upon being combinedwith water, form a slurry that hardens to a concrete upon curing. Cementmaterials include, but are not limited to, hydraulic cement, gypsum,gypsum compositions, lime and the like.

For example a cementitious composition or a cementitious mix or aconcrete composition or a concrete mixture may comprise cementitiousmaterials, optional admixtures, and aggregates. In a non-limitingexample, the cementitious mix or concrete mixture, in certainembodiments, comprises a cementitious composition and the desired amountof water. Non-limiting examples of “cementitious materials” may includehydraulic cement, non-hydraulic cement, pozzolan, granulatedblast-furnace slag, and the like. As used herein, when not otherwisespecified, the term “concrete” may refer to the concrete mixture ineither its fresh/unhardened state or its set/hardened state. A concretein a fresh/unhardened may additionally be referred to as a “freshlymixed concrete,” and a concrete in a set/hardened state may additionallybe referred to as a “hardened concrete.” The term “air entrainment”refers to the inclusion of air in the form of very small bubbles duringthe mixing of concrete. Air entrainment may confer frost resistance onhardened concrete or improve the workability of a freshly mixedconcrete.

The term “granulated blast furnace slag” refers to the glassy, granularmaterial formed when molten blast-furnace slag (a by-product of ironmanufacture) is rapidly quenched. Granulated blast furnace slag may beblended in a pulverized state with Portland cement to form hydraulicmixtures. Granulated blast furnace slag may consist essentially ofsilica, or aluminosilica glass containing calcium and other basicelements. The pulverized form of granulated blast furnace slag may alsobe referred to as “ground granulated blast furnace slag, which is alsoreferred to as “GGBFS” in certain figures provided herein.

“Internal relative humidity” (IRH) of a concrete described herein may bedetermined using the procedure developed by the ASTM committee F.06,also known as the F2170-09 standard entitled “In-Situ Testing ofConcrete Relative Humidity,” which is commonly used in Europe. In anexemplary representation of measuring internal relative humidity, theF-2170-02 test procedure involves drilling holes to a depth equal to 40%of the thickness of the concrete slab, if the slab is drying from onesurface only. The hole is partially lined with a plastic sleeve that iscapped at the entrance of the hole. The apparatus is allowed toacclimate to an equilibrium level for 72 hours prior to inserting aprobe for measuring the internal relative humidity. The floor coveringindustry requires the internal relative humidity reading not to exceed75% prior to application of a flooring adhesive.

The term “pounds per cubic yard,” representing a mass based amount inpounds of a compound per cubic yard of a cementitious mix or a concrete,may also interchangeably be expressed as “lb/yd³” or “pcy.”

The term “pozzolan,” as used herein, refers to a siliceous or siliceousand aluminous material that, by itself, possesses substantially littleor no cementitious value, but when, in particular, in a finely dividedform or an ultrafinely divided form, and in the presence of water,chemically reacts with calcium hydroxide to form compounds possessingcementitious properties. Non-limiting examples of pozzolans include flyash, silica fume, micronized silica, volcanic ashes, calcined clay, andmetakaolin.

As used herein, the term “highly reactive pozzolan” are pozzolans thatreadily react with free lime to form a siliceous binder. Non-limitingexamples of highly reactive pozzolans include silica fume andmetakaolin.

The term “slump,” as used herein when referring to a cementitious mix,means the amount of subsidence of a cementitious composition.Conventionally, slump has been measured by the ASTM C143 (2008 is themost recent specification) standard test procedure, which measures theamount of subsidence of a cementitious composition after removing asupporting cone, as specified in the test procedure.

The term “shrinkage reducing agent,” as used herein, refers to an agentthat is capable of curbing the shrinkage of a cementitious mix as itcures or hardens. Non-limiting examples of shrinkage reducing agentsinclude polypropylene glycol, in particular, polypropylene glycol with anumber average molecular weight of from about 200 to about 1,500, morepreferably, from about 500 to about 1,500, and, even more preferably,from about 500 to 1,000, and derivatives of polypropylene glycol, suchas, for example, copolymers comprising polypropylene glycol(meth)acrylicacid ester and polypropylene glycol mono(meth)allyl ether. Othernon-limiting examples of polypropylene glycol derivatives includepropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether,and the like. In certain preferred embodiments of the invention, certainspecies of polypropylene glycol in the oligomer range may act asanti-shrinkage agents for hydraulic concrete.

Plasticizers, water reducers, or dispersants, as used interchangeablyherein, are chemical admixtures that may be added to concrete mixturesto improve workability. These agents may be manufactured fromlignosulfonates.

The term “superplasticizer,” as used herein, is, generally, a waterreducer, in particular, a high-range water reducer, or an additive thatreduces the amount of water needed in a cementitious mix while stillmaintaining the workability, fluidity, and/or plasticity of thecementitious mix. Superplasticizers may include, but are not limited toformaldehyde condensates of at least one compound selected from thegroup consisting of methylolation and sulfonation products of each ofnaphthalene, melamine, phenol, urea, and aniline, examples of whichinclude metal naphthalenesulfonate-formaldehyde condensates, metalmelaminesulfonate-formaldehyde condensates, phenolsulfonic acidformaldehyde condensate, and phenol-sulfanilic acid-formaldehydeco-condensates. Superplasticizers may also include the polymers andcopolymers obtained by polymerizing at least one monomer selected fromthe group consisting of unsaturated monocarboxylic acids and derivativesthereof, and unsaturated dicarboxylic acids and derivatives thereof.Indeed, in preferred embodiments of the invention, the superplasticizercomprises a polycarboxylate superplasticizer.

The term “polycarboxylate superplasticizer” encompasses a homopolymer, acopolymer, and any combination thereof comprising a polycarboxylic towhich other functional groups may be bonded. Preferably, these otherfunctional groups are capable of attaching to cement particles and otherfunctional groups for dispersing the attached cement particle within anaqueous environment. Specifically, polycarboxylate superplasticizers arepolymers with a carbon backbone having pendant side chains with thecharacteristic that at least a portion of the side chains are attachedto the carbon backbone through a carboxyl group or an ether group. Anexemplary polycarboxylate superplasticizer is given by Formula (I).

-   -   According to Formula (I):    -   D=a component selected from the group consisting of the        structure according to Formula II, the structure according to        Formula III, and combinations thereof.

Additionally, according to Formulas (I), (II), and (III):

-   -   X=H, CH₃, C₂ to C₆ alkyl, phenyl, substituted phenyl;    -   Y₁=H, —COOM; R=H, CH₃;    -   Y₂=H, —SO₃M, —PO₃M, —COOM, —OR₃, —COOR_(S), —CH2OR₃, —CONHR₃,        —CONHC(CH₃)₂, CH₂SO₃M, —COO(CHR₄)_(n)OH where n=2 to 6;    -   R₁, R₂, R₃, R₅ are each independently —(CH₂CHRO)_(m)R₄ random        copolymer of oxyethylene units and oxypropylene units where m=10        to 500 and wherein the amount of oxyethylene in the random        copolymer is form about 60% to about 100% and the amount of        oxypropylene in the random copolymer is from about 0% to about        40%;    -   R₄=H, methyl, C₂ to C₆ alkyl;    -   M=alkali metal, alkaline earth metal, ammonia, amine, methyl, C₂        to C₆ alkyl;    -   a=0-0.8;    -   b=0.2-1.0;    -   c=0-0.5; and    -   d=0-0.5.    -   a, b, c, d, d₁, and d₂ represent the mole fraction of each unit        and the sum of a, b, c, and d is 1.0. The sum of d₁, and d₂ must        be equal to d.

The term “water to cementitious ratio” or “w/c” is defined as the ratioof the mass of the water to the mass of the cementitious materialsimmediately present in the cementitious mix formed upon mixing acementitious composition with the desired amount of water. Generally,when the cementitious composition also comprises a pozzolan, the mass ofthe pozzolan will be added to the mass of the cement in determining thewater to cementitious ratio. Generally, the mass of water used incalculating w/c will not include the water contained in aggregates.

The term “water-cementitious materials ratio” or “w/cm,” which may alsobe referred to as the “water-binder ratio,” is the mass ratio ofavailable water to the amount of cement plus pozzolan plus slag in apaste, mortar, or concrete.

The terms “water vapor emission rate,” “water vapor emissions rate,”“water vapor emission,” and “water vapor emissions,” as may be usedinterchangeably herein, refers to the amount of water, typicallyrepresented as mass, e.g., pounds, emitted from a 1,000 square footsurface area of concrete over a 24 hour period. The water vapor emissionrate, in an embodiment of the invention, may be measured by the testdescribed in ASTM F1869 (2004) entitled the “Standard Test Method forMeasuring Moisture Vapor Emission Rate of Concrete Sub-Floor UsingAnhydrous Calcium Chloride.” ASTM F1869 measures the vapor emission rateby placing an airtight dome containing a specified weight of calciumchloride over the hardened concrete for a defined period of time.

The term “workability,” as used herein, is the relative ease that afreshly mixed paste, mortar, or concrete may be mixed, placed,compacted, and/or finished. The homogeneity of such mixtures may alsoinfluence the workability. In certain cementitious mixtures or mortarmixtures, workability may refer to the consistency and feel of thecementitious mixture or the mortar mixture. The requisite workabilitycan vary based on the use of the cementitious and/or the mortar mixture.For example, depending on the application, the viscosity of the mixturemay vary—e.g., a higher viscosity for applications where rapidflowability is not desired or a lower viscosity where rapid flowabilityis required, such as when performs are used. Of course, as understood inthe art, other physical property parameters may also affect theworkability of the mixture.

Use of Water Soluble Salts to Reduce Internal Relative Humidity andWater Vapor Emission Rate of Concrete

According to some embodiments, the colligative properties of the porewater in concrete is controlled by including one or more water solublesalts, such as one or more alkali metal salts, within the cementitiouscomposition or mix used to manufacture the concrete. The ions releasedfrom the water soluble salt(s) sequester unreacted pore water in thehardened concrete, which reduces the partial pressure of water vapor andthe internal relative humidity (IRH) within the hardened concrete.Reducing the partial pressure of water vapor and IRH in hardenedconcrete in turn reduces the rate of water vapor emission from thehardened concrete, which results in faster drying of the concretesurface. This advantageously permits sooner application of coatings,adhesives, or layers onto the concrete surface as compared to concreteof similar or even lower w/cm known in the art.

In some embodiments, examples of water soluble salts that are effectivein increasing the colligative properties of the remaining pore waterinclude water soluble acetates, formates, sulfates, thiosulfates,nitrates, nitrites, bromides, chlorides, and thiocyanates of one or morealkali metals. For example, soluble alkali metal salts may be selectedfrom salts of lithium, potassium, sodium, and mixtures thereof.

Useful water soluble salts can have minimal reactivity with thehydraulic cement component and provide desired and predictablecolligative properties. Salts that react with hydraulic cement and areat least partially consumed during cement hydration are less able toincrease the colligative property of water because at least some of theions contributed by such salts are consumed and therefore unavailablewhen determining the ratio according to Equation (I). For example, ithas been found that salts of alkaline earth metals are far lesseffective than salts of alkali metals in reducing IRH and the rate ofwater vapor emission and increasing the rate of surface drying ofhardened concrete. It is postulated that alkaline earth metal ions, suchas calcium and magnesium, react with silicate and aluminate ions and aretaken out of solution. As a result, these ions are largely unavailablefor increasing the colligative properties of water.

Based on the principles disclosed herein, the selection of anappropriate quantity of added ionic salt to achieve an IRH of 75-80% orbelow within a predetermined period of time can be determined forconcrete of virtually any w/cm and which hydrates at any known orpredicted rate. For example, a cementitious mixture can be designed toinclude an amount of hydraulic cement, water, and one or more ionicsalts so that water that has not reacted with hydraulic cement at apredetermined time period, such as within 50 days, 45 days, 40 days, 35days, 30 days, 28 days, 25 days, 20 days, 15 days, or 10 days, willcontain a sufficient concentration of ions so as to achieve an IRH of75-80% within the predetermined time period.

In general, the amount of alkali metal salt, such as sodium nitrate, canbe in a range of about 5 lbs per cubic yard (pcy) to about 60 pcy,preferably in a range of about 10 pcy to about 50 pcy, more preferablyin a range of about 20 pcy to about 40 pcy. As will be discussed below,these ranges can be modified to account for the colligative propertiescontributed by any given quantity of other alkali metal salt.

According to some embodiments, a cementitious mix can be designed withan amount of cementitious binder, water, and salt so that the moles ofremaining pore water, divided by the sum of remaining moles of freewater and available moles of dissolved ions, equals 0.75-0.80 or less,which is closely related to the partial pressure of water vapor as wellas the IRH within hardened concrete in accordance with ASTM F-2170. Theaddition of non-volatile and substantially non-reactive (relative tohydraulic cement) salt to the water solution will decrease the IRH andtherefore the water vapor emission according to the number of soluteparticles present. According to some embodiments, there can be enoughsalt and cementitious material to ensure this eventual ratio within aspecified time period or range. However, if the added salt reacts withthe hydraulic cement binder, the concentration of ions within the freepore water contributed by the added salt will be substantially alteredover time by the degree of such reaction, which can add uncertainty andunpredictability to the system.

According to some embodiments, the relationship between the moles ofremaining free water and moles of dissolved ions required to achieve adesired IRH for hardened concrete of 75-80% or less within a specifiedtime period or range can be expressed according to Equation (I):

Moles Free Water÷(Moles Free Water+Moles Dissolved Ions)≦0.75-0.80  Equation (I).

As the dissolved ion concentration increases, the ratio according toEquation (I) also decreases, as do the partial pressure of water vaporand the IRH of hardened concrete. By understanding this relationship,one of ordinary skill in the art can select an appropriate quantity ofone or more salts that will yield hardened concrete that will have apredictable IRH of 75-80% or below within a predetermine time period orrange. In this way, one can avoid adding either too little salt, whichwill yield hardened concrete having a surface that dries too slowly, ortoo much salt, which can cause other problems, such as reduced strengthand/or durability. Another important aspect of Equation (I) is that asthe amount of free water dissipates, either by evaporation of water fromthe concrete surface, continued cement hydration, or both, the numeratordecreases at a faster rate than the denominator because the moles ofsalt ions present remain unchanged. This further accelerates the rate atwhich desired surface drying of the hardened concrete occurs as comparedto the rate of surface drying of concrete at the same or even lower w/cmmade in the absence or inadequate quantity of dissolved ions.

By way of example, assuming that 75-80% IRH is the target, thecementitious mix has a w/cm of 0.35 using 800 lbs of cement, and about70 lbs of free water remain after 75% cement hydration at the target day(e.g., 20 days), including 40 lbs of sodium nitrite within thecementitious mix initially will yield a ratio according to Equation (I)of 0.77, which is closely related to the partial pressure of water vaporand the IRH of the hardened concrete in accordance with ASTM F-2170.Even though moles of a compound are typically measured in grams (e.g.,18 g H₂O per mole; 69 g NaNO₂ per mole), but because units of weightconveniently cancel out in Equation (I), one can assume for simplicitythat molecular weight is measured in lbs per mole rather than grams permole (e.g., 18 lbs H₂O per mole; 69 lbs NaNO₂ per mole). Thus, the molesof remaining water can be assumed to be 70 lbs÷18 lbs per mole=3.89moles. Similarly, the moles of sodium nitrite can be assumed to be 40lbs÷69 lbs per mole=0.58 mole sodium nitrite. Because sodium nitritecontributes two moles of ions per mole of dissolved compound, the numberof moles of combined sodium (Na+) and nitrite (NO₂−) ions is2×(40÷69)=1.16 mole of ions. Thus, the ratio of 0.77 is determinedaccording to Equation (I) as follows:

3.89 Moles Free Water÷(3.89 Moles Free Water+1.16 Mole of Ions)=0.77.

By way of further example, in the case where the amounts of water andcement in a concrete composition are selected so that, at a preselectedtime period (e.g., 28 days), the amount of unreacted water remaining inthe pores after hydration of the cement is 65 lbs. per cubic yard (yd³)of concrete, including 40 lbs. of sodium nitrite per cubic yard (yd³) ofconcrete would yield a ratio of 0.76 according to Equation (I). Thus,the ratio determined by Equation (I) for 65 lbs. of remaining water(65/18=3.61 moles pore water) and 40 lbs. of sodium nitrite ions(40/69×2=1.16 moles of ions) is as follows:

3.61 Moles Water÷(3.61 Moles Water+1.16 Moles Ions)=0.76

When using multiple salts, one would simply add up the sum of the molesof ions contributed by all of the salts.

In contrast, concrete made in the absence of added dissolved ionscontributed by sodium nitrite or other water soluble salt will have aratio approaching 1 (i.e., 3.89 moles free water÷(3.89 free water+0moles ions)=1). Such concrete would be expected to have substantiallyhigher IRC, water vapor emission rate, and surface moisture at thetarget day.

Another important aspect of Equation (I) is that it is useful indetermining the appropriate quantity (e.g., weight) of salt to be addedto a cementitious or concrete composition that will yield the desiredratio independently of molecular weight and/or the number of ionscontributed by a particular salt compound. It is also useful indetermining an appropriate salt concentration independently of aggregatespecific gravity, such as when a lightweight aggregate is use. In fact,when using a porous lightweight aggregate that reduces the weight of acubic yard of concrete but increases the total amount of water and w/cmrequire to provide a desired flow, the weight percent of salt within thecementitious or concrete composition will typically be substantiallygreater than when using a normal aggregate. By relating the amount offree water, dissolved ions, and expected IRH within a predetermined timeperiod or range, Equation (I) normalizes for such differences inaggregate specific gravity, free water content, w/cm, and the molecularweight of salt.

With respect to molecular weight, for example, the appropriate weightquantity of sodium nitrite that should be added to yield hardenedconcrete having a desired IRH of 75-80% or below within a predeterminedtime period or range will be different than the weight quantity of saltshaving different molecular weight and/or which contribute a differentnumber of dissolved ions. This amount can be normalized for virtuallyany other binary alkali metal salt that is assumed to contribute 2 ionsper molecule by dividing the molecular weight of the alkali metal saltby the molecular weight of sodium nitrite to obtain a normalizationratio and multiplying this ratio by the amount of sodium nitrite. Thus,the amount of binary water soluble alkali metal salt that is equivalentto a given weight of sodium nitrate would be determined according toEquation (II) as follows:

Weight (NaNO₂)×(MW Salt÷69)=Equivalent Weight Salt   Equation (II).

Due to differences in intermolecular attraction (van der Waals forces)the salt water activities can vary from this assumption, particularlywith more complex molecules. For example, sodium thiosulfate hydrate(Na₂S₂O₃.5H₂O) contains three ions (2 sodium ions and 1 thiosulfate ion)but empirically contributes somewhat more than 3 ions when dissolved inthe free water (perhaps because the sodium ions sequester a differentnumber of water molecules than the thiosulfate ion). When a saltempirically contributes a different number of available ions forsequestering water, Equation (II) can be generalized to account for suchdifferences according to Equation (III):

Weight (NaNO₂)×(MW Salt/ions per mole÷69/ions per mole)=EquivalentWeight Salt   Equation (III).

Equation (II) is therefore the special case of Equation (III) where bothalkali salts contribute 2 moles of ions per mole of compound that can beused to sequester water within hardened concrete and the divisor 2simply cancels out.

Using the foregoing principles, and assuming that sodium thiosulfatehydrate has a molecular weight of 248 lbs per mole and contributes 3moles of ions, 95.8 lbs of sodium thiosulfate would contribute the samenumber of ions as 40 lbs of sodium nitrate according to Equation (III):

40 lbs sodium nitrite×(248/3÷69/2)=95.8 lbs sodium thiosulfate.

According to Equation (I), 95.8 lbs of sodium thiosulfate wouldtherefore yield the same ratio 0.77 as 40 lbs of sodium nitrate:

70/18÷(70/18+3×95.8/248)=0.77

Equation (II) or (III) can be used to construct a concentration rangefor alkali metal salts other than sodium nitrite. For example, if theappropriate amount of sodium nitrate required to yield concrete having adesired IRH of 75-80% or below within a predetermined time period is ina range of about 5 lbs to about 60 lbs per yard of concrete, theappropriate amount of sodium thiosulfate would be in a range of about 12lbs to about 216 lbs per yard of concrete, as determined by applyingEquation (III) to each range endpoint:

5 lbs (248/3÷69/2)=12 lbs

60 lbs (248/3÷69/2)=144 lbs.

In general, for any alkali metal salt, a desired concentration rangecorresponding to a range of A pcy to B pcy of sodium nitrate can beexpressed as follows:

A×(MW/IPM÷69/2) pcy to B×(MW/IPM÷69/2) pcy

where MW=molecular weight of alkali metal salt and IPM=ions per mole.

According to some embodiments, the amount of alkali metal salt,expressed in relation to the aforementioned ranges for sodium nitrate(i.e., about 5 pcy to about 60 pcy, or about 10 pcy to about 50 pcy, orabout 20 pcy to about 40 pcy), can be in a range of about 5(MW/IPM÷34.5) pcy to about 60 (MW/IPM÷34.5) pcy, preferably in a rangeof about 10 (MW/IPM÷34.5) pcy to about 50 (MW/IPM÷34.5) pcy, morepreferably in a range of about 20 (MW/IPM÷34.5) pcy to about 40(MW/IPM÷34.5) pcy.

Cementitious and Concrete Compositions

Disclosed herein are composition and methods for maintaining or alteringthe ionic concentration of the water in concrete and/or lightweightaggregates in order to accommodate an amount of water in excess of thatneeded to react with the cements, which is typically required to providedesired workability. In general, concrete requires water for cementhydration as well as water of convenience to provide workability andfacilitate placement. The water of hydration must typically be consumedand the water of convenience largely evaporated before proper permanentbonding of water-based adhesives can be assured. Unfortunately, the timenecessary to accommodate the requisite evaporation and hydration can beapproximately one month per inch of concrete floor depth. Placement offloor coverings using current water-soluble adhesives must often bedelayed until the residual concrete water has sufficiently dissipated toprovide an internal relative humidity (IRH) of no more than about 75-80%in accordance with ASTM F-2170-09.

Generally, water vapor emission is proportional to the state of relativedryness of the body of the concrete structure. Once isolated fromexternal sources of water, water vapor emissions are derived from theamount of water that is used in excess of that needed to harden thecementitious materials, i.e., the water of convenience. Depending uponthe atmospheric temperature and humidity at the surface and thethickness of the concrete, the elimination of excess water through watervapor emissions can take several months to reach a level that iscompatible with the application of a coating or an adhesive (e.g., toreduce risk of delamination).

A lightweight coarse aggregate may be designed into a concrete mix toreduce building dead load and increase fire resistance. This lightweightmaterial commonly comprises an expanded shale, clay, or slate with adensity of about 1/2 that of normal stone coarse aggregate and iscapable of producing lightweight concrete that weighs from 800 to 1000pounds less per cubic yard. The weight reduction provided by thelightweight aggregate is achieved by creating a highly porous internalstructure in the lightweight aggregate that can, however, absorb up to30% water by weight. This water is in addition to the normal waterrequired to provide desired slump and can impart additional water to theconcrete mix equal to 2 to 3 times of the amount of water that mustnormally evaporate, thereby increasing the time to dry for adhesive orepoxy application by a similar amount. This additional time is beyondthe tolerance of many fast-track construction schedules and increasesthe likelihood of bond failure and delamination should this drying timebe truncated.

In some embodiments, water soluble salts may be used to alter the ionicconcentration of the water in concrete and thereby control the internalrelative humidity of concrete within a predetermined time period orrange. According to one embodiment, one or more water soluble salts areincorporated into the cement paste upon mixing the cementitiouscomponents together. According to another embodiment, one or more watersoluble salts can be incorporated into the pores of a lightweightaggregate and thereby indirectly incorporated into the cement paste whenmixing the cementitious components together. Either method allows forimproved water retention within the fine pores of the cementitiousmaterial over time, improved initial concrete workability, and limitedwater-vapor emission, enabling the resulting low-density concretes toattain a desired relative humidity in a shorter time. If water is madeavailable to the mix by virtue of its being absorbed and then desorbedby lightweight aggregate, then its introduction should be anticipated byadjusting the ionic concentration of salt added to the aggregates toyield a cement paste having a desired ionic concentration.

According to certain embodiments of the invention, autogenous and dryingshrinkage of concrete may be substantially reduced or, in certainembodiments, eliminated altogether. Finer cements, slags and pozzolansmay lead to the production of smaller pores in thecalcium-silicate-hydrate (CSH) gel. This results in increased autogenousand drying shrinkage due to the magnified effect of surface tension aspore radii diminish (Young-Laplace equation or Kelvin). As the cementparticles hydrate, they consume about 20% of their weight in water andat the same time lose about 10% of their volume, resulting in chemicalshrinkage or autogenous shrinkage. The large capillaries dry first,resulting in a shift to progressively smaller capillaries and gel pores.

Introducing salt into the capillaries and gel pores of cement pastereduces the relative humidity (RH) within concrete by virtue of the salteffect on relative humidity and its effect on the micro pore surfacetension and pressure differential across the meniscus. As a consequenceof lower w/cm and smaller pores, high performance concrete in general,and fast drying normal-weight aggregate concretes specifically, sufferfrom increased autogenous and drying shrinkage resulting in a potentialfor micro cracks and macro cracks leading to early deterioration. Thisphenomenon can be utilized to advantage in several ways. First, thesmall pores thus formed reduce the internal relative humidity (IRH) ofconcrete, particularly in the presence of increasing salt concentration.Second, if the lightweight coarse aggregate is water soaked with liquidwater (not vapor) into its capillaries, then its introduction into asoluble salt treated mortar will result in an osmotic pressure. Thispressure drives water and water vapor into the hydrated cement voidsspace, which offsets the tendency of the paste to undergo autogenous anddrying shrinkage. This is a surprising and unexpected result.

It is conventionally believed that small particles (e.g., light weightfines) are needed for moisture sourcing dispersion. However, accordingto certain embodiments of the invention, well soaked coarse lightweightaggregate in a salt-dosed HPC mix may “eliminate” drying and autogenousshrinkage. If a lightweight concrete is pumped, for instance, theexpected pressure may diminish the osmotic effect by forcing salts intothe lightweight aggregates. The drying shrinkage attenuation will remainbut autogenous shrinkage may return to significant, but diminished,extent.

This insight on shrinkage leads to new large volume uses for concrete.For example, in warehouse floor slabs or stores where concrete jointsmust be dowelled for load transfer, curling (top to bottom of slabdrying differential) pulls the slab off subgrade support and createssurface irregularities. Both shrinkages contribute to this negativeeffect. Now, in a temperature-controlled environment, expanses ofconcrete can be longer than 100 feet without a joint, leading to reducedinstallation expense in reinforcing steel and jointing. This is animportant improvement over conventional concrete methodologies forproducing fast drying concrete, particularly those which rely on largedoses of superplasticizer and low w/cm (less than 0.4), which producelarge increases in autogenous and drying shrinkages.

In certain embodiments of the invention, the water vapor emission rate,as well as other properties, such as, for example, internal relativehumidity, a required amount of water content of the concrete, and therequired water to cementitious ratio, are determined by a process orprocedure as provided in U.S. Pat. No. 8,220,344 entitled “Method forEstimating Properties of Concrete” fully incorporated herein byreference. The process or procedure, otherwise known as the “mortarmethod,” comprises a procedure for preparing a representative mortarsample, typically substantially free of any coarse aggregate, having awater to cementitious ratio that is consistent with that of the concreteto be proportioned. Preferably, the prepared mortar mixture to be testedwill have substantially the same ratio of compounds of the cementitiousmix. The prepared sample mixture is cast into a small mold having apreferred surface to volume ratio of about 0.67 in−1 (6 inch×6 inchpanels having a volume of about 54 cubic inches) to simulate the dryingexperienced by concrete that is exposed to the atmosphere at only onesurface. The mortar is cast to a depth, which preferably approximatesthe depth of concrete that is immediately reactive to atmospherictemperature and moisture gradients. In certain embodiments of theinvention, the mortar is cast to a depth of about 1½ inches. The castsamples of mortar are cured and periodically weighed at measuredintervals in order to determine the amount of daily water loss. Thewater vapor loss is used to estimate the drying rate or some otherproperty of a concrete based upon a correlation.

Embodiments disclosed herein relate to cementitious compositions,specifically to cementitious compositions that yield hardened concretehaving decreased or attenuated rate of water vapor emission. Thecementitious compositions are formulated to include hydraulic cement andat least one water soluble salt as water vapor attenuation agent.Non-limiting examples of water soluble salts useful as water vaporattenuation agents an alkali metal salts, examples of which includealkali metal formates, alkali metal acetates, alkali metal nitrates,alkali metal nitrites, alkali metal halides, alkali metal thiosulfates,and alkali metal thiocyanates. Water soluble alkali metal salts may beselected from salts of lithium, potassium, sodium, and mixtures thereof.

Other water vapor attenuation agents can be used in addition to the oneor more water soluble salts. Examples of other water vapor attenuationagents include superplasticizers, such as polycarboxylatesuperplasticizers; finely divided particulate materials, such as highlyreactive pozzolans; and shrinkage reducing agents.

In some embodiments, the cementitious composition may include a cementreplacement, such as a finely divided material having a particle sizeless than about 75 microns. Finely divided pozzolans can react withwater and calcium ions released during cement hydration to formdensifying calcium silicates. In some embodiments, the pozzolan maycomprise any natural pozzolan; any artificial pozzolan, such as fly ash;and any combination thereof. In yet other embodiments of the invention,the finely divided material comprises a ground slag, such as groundgranulated blast furnace slag.

Another aspect of the invention provides a method of manufacturingconcrete having improved water retention and surface dryingcharacteristics, comprising: (1) preparing a fresh cementitious mixtureby blending an aggregate (e.g., porous lightweight aggregate) withhydraulic cement, water and one or more water soluble salts; (2)allowing water to react with hydraulic cement to form hydrationproducts, which hardens the fresh concrete mixture to form hardenedconcrete; and (3) ions from the salt sequestering and retaining waterwithin fine capillary pores of cement paste. The salt ions inhibitdiffusion of excess water not used in hydration of cement from the poresof the cement paste, thereby permitting the surface of hardened concreteto more quickly achieve a desired dryness compared to hardened concretemade without using the salt.

Examples of metal cations that may be suitable for salts in certainembodiments of the invention include, but are not limited to, lithium,potassium, sodium, and combinations thereof. Examples of anions that maybe suitable for salts in certain embodiments of the invention include,but are not limited to, formate, acetate, sulfate, thiosulfate, bromide,chloride, thiocyanate, nitrite, nitrate, and combinations thereof.Further pursuant to these certain embodiments useful salts include, butare not limited to, sodium formate (HCOONa), sodium acetate (NaAc),sodium nitrate (NaNO₃), sodium nitrite (NaNO₂), sodium sulfate (Na₂SO₄),potassium sulfate (K₂SO₄), sodium chloride (NaCl), sodium silicate(NaSiO₃), sodium thiosulfate hydrate (Na₂S₂O₃.5H20), and sodiumthiocyanate (NaSCN).

Without intending to be bound by theory, an advantage to incorporatingone or more water soluble salts into cement paste to yield concretehaving a faster drying surface may be the sequestration of most of themix water in small pores that exist within the concrete, particularlywithin cement paste. In some embodiments, about 50% of the pastefraction of concrete can be made up of capillary and calcium silicategel pores. Higher cementitious concretes can be about ⅓ by volume, or 9cubic feet of cement paste out of 27 cubic feet in a cubic yard, withthe balance being made up of aggregate, according to certain embodimentsof the invention. In a properly designed mix, according to certainembodiments of the invention, pore volume can, therefore, account for upto 4½ cubic feet of the water (280 pounds).

A problem that may conventionally be experienced with producing micropores of sufficient quantity to absorb and hold this water in anon-evaporable state is that the size of the pores is typically afunction of the water-cementitious (w/cm) ratio. It is generallyaccepted by a person having ordinary skill in the art that pore sizedoes not substantially exist or become discontinuous, even with extendedcure times, above water-cementitious ratios of about 0.6 or 0.7. As thewater-cement ratio decreases from these levels, smaller pores may beformed. When the water-cement ratio drops below 0.4, sufficient micropores are usually present to impact internal relative humidity and thusmeasurably affect drying. This lower level of water dictates a verystiff (low slump) workability that will not pump easily unless augmentedwith substantial amounts of super-plasticizer, which is tolerable instandard weight concrete but, as previously pointed out, is difficult tomanage in lightweight concrete.

Physical upper limits exist on cementitious levels as well, since theirrelative fineness begins to require increasing amounts of water afterthe content surpasses about 800 pounds per cubic yard. In the usualproportions found in lightweight concrete, the aggregate alone can holdfrom 70 pounds to as much as 250 pounds of water. The dichotomy thenbecomes: more cementitious binder cannot be added nor can more watereasily be withdrawn.

In some embodiments, the cementitious compositions can include compoundsor be compounded to demonstrate a number of advantageous properties orfeatures. In an embodiment of the invention, the cementitiouscompositions include compounds or are compounded to reduce the amount ofwater of convenience. In other embodiments of the invention, thecementitious compositions include certain compounds and are compoundedin such a way so as to augment the effectiveness of a superplasticizer.In other embodiments, the cementitious compositions increase packing, ordecrease intersticial spacing, of an aggregate that has been included inthe composition, thereby effectively reducing permeability. In stillother embodiments, the cementitious compositions include compounds orare compounded such that the cements that are included in thecomposition consume much of the water present, preferably in such amanner so as to reduce excessive production of reaction heat. In certainembodiments, a concrete composition has an advantage of improvedworkability. In certain embodiments, a concrete composition of theinvention has a faster surface drying rate.

In some embodiments, the resulting concrete composition forms a concretehaving some of the aforementioned properties. In other embodiments ofthe invention, the resulting concrete composition forms a lightweightconcrete having at least some of the aforementioned properties. Incertain embodiments of the invention, the resulting concrete compositionforms a low density concrete have at least some of the aforementionedproperties.

The inventive cementitious compositions, without intending to be boundby theory, offer improvements over other cementitious compositions knownin the art by providing a concrete that demonstrates a reduction in theamount of time needed to achieve a desired water vapor emission rate,otherwise known herein as an “attenuated water vapor emission” or“decreasing the rate of water vapor emission.” In an embodiment of theinvention, the cementitious composition having a decreased rate of watervapor emission from concrete achieves a water vapor emission rate ofbetween about 3 lb/1000 ft²/24 h to about 5 lb/1000 ft²/24 h in lessthan or equal to about 50 days, less than or equal to about 36 days,less than or equal to about 30 days, less than or equal to about 28days, less than or equal to about 25 days, less than or equal to about21 days, less than or equal to about 18 days, less than or equal toabout 15 days, less than or equal to about 12 days, less than or equalto about 10 days, and less than or equal to about 7 days.

In some embodiments, the cementitious compositions provide a reductionin the number of days needed to achieve an internal relative humidity of75-80% in accordance with ASTM F-2170. The cementitious compositions,according to certain embodiments of the invention, will produce ahardened concrete that has 75-80% internal relative humidity in lessthan about 50 days; preferably, less than about 36 days; morepreferably, less than about 30 days; even more preferably, less thanabout 28 days; still even more preferably, less than about 22 days; and,yet still even more preferably, less than about 17 days. In someembodiments, the cementitious compositions offer the improvement ofproviding a finished concrete that allows the application of coatingsand adhesives much sooner than concretes produced by conventionalcementitious compositions known in the art.

In some embodiments, the cementitious compositions can be used toprepare a concrete structure for a flooring application. While notintending to be bound by theory, upon being mixed with water, thecementitious compositions consume and emit water in such a manner thatlittle water remains in the hardened concrete to disturb water-basedglues that are affixed to or coated onto the hardened concrete, whichact as floor coverings. The inventors have discovered that it isimportant not only to reduce the amount of excess water in acementitious mix, but to also include certain compounds in theformulation and to compound the formulation of the cementitiouscompositions in such a way that excess water is more favorably andrapidly sequestered than that which can be achieved by conventionalcementitious compositions.

In various embodiments of the invention, the cementitious compositionsmay include compounds or be compounded to demonstrate a number ofadvantageous features and/or properties. In an embodiment of theinvention, the cementitious compositions include compounds or arecompounded to reduce the amount of water of convenience. In otherembodiments of the invention, the cementitious compositions includecertain compounds and are compounded in such a way so as to augment theeffectiveness of a superplasticizer. In yet other embodiments of theinvention, the cementitious compositions increase packing, or decreaseinterstitial spacing, of an aggregate that has been included in thecomposition, thereby effectively reducing permeability. In still yetother embodiments of the invention, the cementitious compositionsinclude compounds or are compounded such that the cements that areincluded in the composition concentrate the compounds (salts) in thewater enhancing their colligative properties.

In preferred embodiments, the cementitious compositions include a watervapor attenuation agent, as further described herein. In a preferredembodiment of the invention, the cementitious composition is formulatedto include a water vapor attenuation agent that is a water immobilizeri.e., a compound that reduces mix water evaporability. Without intendingto be limiting, compounds that reduce water evaporability or increasecolligative properties are particularly useful in embodiments of theinvention when a water to cement ratio higher than about 0.3, or more,is needed to achieve a certain desired degree of plasticity orworkability for pouring a cementitious mix produced from thecementitious composition. Highly reactive pozzolans can assist inscavenging excess water.

Furthermore, it has been found that a cementitious mix made withcementitious compositions having a highly reactive pozzolan, withoutlimitation, such as metakaolin and/or silica fume, continue to hydrateat relative humidity levels substantially below those cementitious mixesformed from a cementitious composition of a Portland cement, slag, andother pozzolans lending to their ability to scavenge water. In anembodiment of the invention, the water vapor attenuation agent of thecementitious composition is a highly reactive pozzolan; and anycombination thereof having a concentration in the range of from about0.5 wt % to about 25 wt %, preferably, from about 3 wt % to about 18 wt%, and, more preferably, from about 3 wt % to about 13 wt % based on thetotal weight of the cementitious composition.

In some embodiments, cementitious compositions having a water vaporattenuation agent that is considered a water scavenger, a highlyreactive pozzolan, and any combination thereof, are capable of consumingat least about 5, at least about 10, at least about 20, at least about30, at least about 40, and at least about 50 pounds of water per cubicyard of concrete over conventional cementitious mixes.

In some embodiments, cementitious compositions having a water vaporattenuation agent that is considered a water scavenger, which mayinclude an ultrafine calcium carbonate, preferably, having an averageparticle size of less than or equal to about 3 microns; a highlyreactive pozzolan; and any combination thereof, are capable of consumingat least about 5, at least about 10, at least about 20, at least about30, at least about 40, and at least about 50 pounds of water per cubicyard of concrete over conventional cementitious mixes.

In other embodiments, smaller pore formation can be provided in thefinished concrete. Smaller pore formation, depending on the formulationof the cementitious mix, may lead to concrete having decreased rate ofor an attenuated water vapor emission earlier in the curing or hardeningprocess. Without intending to be bound by theory, a reduction in poresize results in an inhibition of capillary water movement, which maylead to lower apparent internal relative humidity and a reduction in thewater vapor emission rate.

In certain embodiments, the cementitious compositions may comprisesoluble ionic salts. Without intending to be bound by theory, solubleionic salts may sequester water based on the principle that water vaporconcentration, and, therefore, the relative humidity over a saltsolution is less than that over that of pure water because of itscolligative property. Water may be present in both the gas and theliquid phase, whereas the scarcely volatile salt molecules may only bepresent in the liquid phase. The salt ions dilute the water and hinderthe escape of water molecules into the air—i.e., the presence of thesalt ions changes the equilibrium between the vapor and liquid phase.The rate of return of water molecules to the liquid surface isproportional to their concentration in the gas, where there are no saltions to interfere. The system therefore adjusts to equilibrium wherethere are fewer water molecules in the air than there would be over apure water surface. The relative humidity is therefore lower than 100%.Francois-Marie Raoult developed the following formula to represent thisconcept:

P=p* _(i) x _(i)

-   -   where,    -   P=total vapor pressure    -   p*_(i)=vapor pressure of water    -   x_(i)=moles of water/(moles of water+moles of salts)    -   If, on the other hand, a binary ionic salt such as sodium        acetate (anhydrous) is used, then:    -   x_(i)=moles of water/(moles of water+2* moles of salt)

According to certain exemplary experimental results, the closeness ofresults calculated by Raoult's law is shown by the data in Table 2.

The salts of Table 2 were placed into aqueous solutions in a closedcontainer with an inserted humidity probe and allowed to stabilize over48 hours. Analogizing this data to concrete, if it is assumed that thecementitious materials contain 0.6% alkali as Na₂O then in an 800 poundcementitious mix, for example, the moles of NaOH would be as follows:

Na₂O+H₂O=2 NaOH, 0.006×800×80/62=6.2/40=0.155

TABLE 2 NaNO₂ NaNO₃ NaC₂H₃O₂ Raoult Solution Solution SolutionCalculated RH RH RH RH 1 molar 93 93 93 97 3 molar 82 89 86 90 6 molar75 80 75 82 RH = relative humidity

Additional salt addition may also raise the surface tension of water byabout 5% and create a thickening of the water-ionic layer along thewalls of the pores, thus effectively reducing their volume and providingan enhancement to negative pore pressure forecast by the Kelvinequation. The Kelvin equation can be used to describe the phenomenon ofcapillary condensation due to the presence of a curved meniscus,according to the following formula:

${\ln \frac{P_{v}}{P_{sat}}} = {- \frac{2\; H_{\gamma}V_{l}}{RT}}$

-   -   where,    -   P_(ν)=equilibrium vapor pressure    -   P_(sat)=saturation vapor pressure    -   H=mean curvature of meniscus    -   γ=liquid/vapor surface tension    -   V_(i)=liquid molar volume    -   R=ideal gas constant    -   T=temperature

An additional enhancement, although relatively smaller than the previousmentioned effects, is the expansion of the water lubrication capabilityby salt addition of a salt. The data in Table 3 was obtained by addingseveral separate salts to water and observing the expansion ordisplacement that occurred.

TABLE 3 displacement % 1 molar 2.4 3 molar 5.2 6 molar 16

The inventors have found that the combination of the sum of theseeffects permits the construction of a concrete with enhanced capacity tosequester water in a non-evaporable state. As the data set forth inTables 4 and 5 demonstrate, excursions well beyond the maximum 0.4water-cement ratio typically required for fast drying and HPC concreteare now possible.

TABLE 4 Type IV Grade 120 pounds pounds pounds Lightweight Pounds poundspounds Type F ASTM c33 ASTM c33 ASTM c330 moisture Mix cement slagpounds Sand #67 Stone ½″ Lightweight % dry wt Water Mix 1 300 300 0 14001700 0 n/a 325 Mix 2 300 300 0 1400 1700 0 n/a 325 Mix 3 300 300 0 14001700 0 28.2 325 Mix 4 400 400 0 1400 0 750 28.2 325 Mix 5 400 400 0 14000 750 28.2 325 Mix 6 400 400 0 1400 0 750 28.2 325 Mix 7 600 0 200 14000 750 28.2 325 Mix 8 600 0 200 1400 0 750 28.2 325 Mix 9 300 300 0 14001700 0 n/a 325

TABLE 5 Days to Total W/Cs Salt Salt Salt Salt ASTM F (Includes NaOHNaNO₂ NaNO₃ NaC₂H₃O₂ 2170 lightweight pounds pounds pounds pounds 75%IRH W/Cs water). Mix 1 0 0 0 0   50+ 0.54 0.54 Mix 2 0 0 0 20 23 0.540.54 Mix 3 4 0 0 20 14 0.54 0.54 Mix 4 0 0 0 0   50+ 0.61 Mix 5 0 20 0 019 0.61 Mix 6 4 20 0 0 12 0.61 Mix 7 4 20 0 0 45 0.61 Mix 8 0 0 0 0 100+0.61 Mix 9 0 0 35 0 26 0.54

As can be readily observed, the drying time with both stone andlightweight concretes can be considerably shortened by increasing theconcentration of single or combinations of salts. Care should beexercised to ensure that the salts do not cause efflorescence, reactadversely with the concrete hydration, or strongly deliquesce.

The preponderance of the aggregate and mix water sequestered within thetreated concrete at an internal relative humidity of 75% as is shown inthe data set forth in Table 6.

The data in Table 6 demonstrates that the amount of water remaining infast-dry design lightweight concrete has been reduced to 7.6 ft³ afterreaching an internal relative humidity of 75%.

TABLE 6 Mix cement 250 250 F. pounds slag 550 Oven Loss: 361 sand 1400Evaporation: 25 Lightweight 1006 Retained in 116 Concrete: Water 325Total 502 Lightweight 21.4% of dry Wt. Moisture: mix water 0.41 % WaterW/Cs Total W/Cs 0.63 retained in concrete 95 NaNO₂ 35 cubic feet 7.6water retained in concrete @ 75% internal RH: Total Water: 502Chemically bound 23% Water:

The laboratory work with this system showed an unusual result in thatevaporation pans of treated concrete made from the same samples of salttreated concrete reflected the same pattern as the internal relativehumidity (IRH) specimens. It can be concluded from this that theevaporation rate is related to the formation of a discontinuous poresystem and therefore indicative of small pore formations in thecapillary system.

The low water vapor emission rate and relatively fast attainment of 75%IRH in lightweight concrete led to an investigation of volume change inthis type of concrete. Data relating to shrinkage is set forth in Table7.

TABLE 7 Dry Dry lbs lbs Normal Modified LW HPC Cement 600 400 GGBFS 0400 Type F Ash 200 0 Sand 1250 1400 1/2″ lightweight 0 850 Stone 1700Water 325 325 plasticizer 14 oz. 16 oz. W/C 0.41 0.41 PCF 151 126 AE1.30% 1.3% Total W/C 0.43 0.63 Agg. Water 13 186 NaNO₂ 0 20 NaOH 0 4 7day autogenous % 0.016 −0.001 28 Day air dry % 0.041 −0.003 Total %0.057 −0.004

The volume change was measured in standard ASTM C-157 molds during thefirst 24 hours. One end plate was anchored and the other plate was leftfree to move. The mold was lined with thin plastic to minimize friction.An additional stainless steel stud was screwed into the free end plateso that it passed through the end of the mold. A magnetically held dialmicrometer stem was positioned to indicate any bar movement followinginitial set. The concrete bar was sealed in plastic after casting. At 24hours the dial was read and the bar stripped from the mold, wrappedcompletely in 3 layers of plastic sheet with the embedded steel studsprotruding. The bar was then measured in standard ASTM C-157 devices. At7 days after casting the bar was again measured. Any change was added tothe 24 hour reading and considered to constitute autogenous shrinkage.The bar was then unwrapped and allowed to dry for an additional 28 daysin a standard lab environment. Drying shrinkage was computed bycomparing the 7 day dimension to the one obtained after 28 days ofdrying. A negative number indicates expansion.

The lightweight concrete contains plain water while the surroundingmortar contains about a 1.1-1.3 molar initial concentration of binarysalts. As the cement hydrates and this concentration increases, asemi-permeable gel membrane is grown around the coarse lightweightaggregate particles. The salt imbalance causes sufficient osmoticpressure to fill in the voids that normally develop due to chemicalshrinkage and thereby prevents autogenous shrinkage. This type ofconcrete formulation loses very little water before coming toequilibrium with a 50% RH environment. The lightweight water reserve isknown to replenish this loss as well.

The osmotic pressure 7E, is given by van't Hoff s formula, which isidentical to the pressure formula of an ideal gas:

π=cRT

-   -   where,    -   c=molar concentration of the solute,    -   R=0.082 (liter·bar)/(deg·mol), is the gas constant, and    -   T=temperature on the absolute temperature scale (Kelvin).

For example, water that contains 78 gram/liter of sodium nitrite(NaNO₂), and sodium hydroxide (NaOH) typical of the mix in the aboveexample, has an ionic concentration of c=2.39 mol/liter. Inserting thevalues into the van't Hoff formula, for the ambient temperature T=396 K,yields the osmotic pressure:

π=2.39·0.082·296=58 bar=841 psi

The water pressure could have destructive consequences if its sourcewere to be unlimited, but the lightweight holds a finite amount ofrelatively pure solvent and removal of water results in a negativepartial pressure in the lightweight particle sufficient to establishequilibrium.

The data in exemplary samples of Table 8 illustrate the effect of theaddition of salt to stone and lightweight aggregate concrete. Theevaporation rate was measured by weighing 6×6 inch pans of concrete asthey dried. Note that the addition of salt lowered the evaporation rate.

TABLE 8 Cement 300 300 250 250 lbs GGBFS 300 300 550 550 lbs Sand 14001400 1400 1400 lbs 1/2″ lightweight 0 0 850 850 lbs Stone 1700 1700 0 0lbs Water 325 325 325 325 lbs plasticizer 6 6 16 16 oz W/Cs 0.54 0.540.41 0.41 lb/lb Moisture loss to 73 31 12 14 lbs 75% IRH NaNO₂ 0 20 3535 lbs NaOH 0 4 0 0 lbs

Another aspect of the invention involves provides a cementitiouscomposition or concrete composition having water soluble salts in thecement paste and cementitious mixtures by infusing a porous lightweightaggregate with a water-salt solution to yield a treated porouslightweight aggregate having improved water saturation and waterretention. According to an embodiment of the invention, it may beadvantageous and desirable to anticipate and accommodate the amount ofwater available in excess of that needed to react with the cements, aswell as the resulting salt concentration in the cement paste. If wateris made available to the mix by virtue of its being absorbed and thendesorbed by lightweight aggregate, then the introduction of water shouldbe anticipated by adjusting the ionic concentration.

According to an embodiment of the invention, the porous lightweightaggregates may be treated with salts or solutions of salts. The treatedaggregates may be mixed with cementitious materials, admixtures, andwater to manufacture various concrete mixtures, which can be used inapplications where ordinary low-density concretes are suitable. Incertain embodiments, pretreatment of lightweight aggregates permitsretention of water in their small capillary pores, thus retaining waterduring storage, as well as facilitating rapid large capillary porerewetting when making fresh concrete.

One method, according to an embodiment of the invention, involvesinfusing porous lightweight aggregates with water to yield treatedporous lightweight aggregates having improved water saturation and waterretention. This method may comprise providing a porous lightweightaggregate having pores and capillaries, and treating the porouslightweight aggregate with an aqueous solution comprising water and atleast one salt. Without intending to be bound by theory, the salt mayenhance penetration of aqueous solution into pores and capillaries ofthe porous lightweight aggregate and help retain water within thecapillaries over time. In various embodiments of the invention, theporous lightweight aggregates are treated with salts by soaking orquenching the aggregates in an aqueous solution of the salt.

A porous lightweight aggregate having improved water saturation andwater retention can be manufactured according to a method comprising:(1) providing a porous lightweight aggregate having pores andcapillaries and (2) treating the porous lightweight aggregate with anaqueous solution comprising water and at least one salt. The at leastone salt enhances penetration of the aqueous solution into the pores andcapillaries of the porous lightweight aggregate and helps retain waterwithin the capillaries over time, as compared to the porous lightweightaggregate treated with only water without the salt.

Another aspect of the invention provides a method of manufacturingfreshly mixed concrete having improved workability comprising: (1)providing a porous lightweight aggregate infused with an aqueoussolution comprising water and at least one salt, and (2) preparing afresh concrete mixture by blending the porous lightweight aggregate withhydraulic cement and water. Without intending to be bound by theory, thesalt may enhance penetration of the aqueous solution into pores andcapillaries of the porous lightweight aggregate and help retain waterwithin the capillaries over time compared to the porous lightweightaggregate only treated with water without the salt. The treated porouslightweight aggregate can lead to enhanced workability of fresh concretecompared to fresh concrete made using the porous lightweight aggregatewithout treatment with the salt.

Another aspect of the invention relates to a method of manufacturinglow-density hardened concrete having improved drying characteristics,comprising: (1) providing a porous lightweight aggregate infused with anaqueous solution comprising water and at least one salt; (2) preparing afresh concrete mixture by blending the porous lightweight aggregate withhydraulic cement and water; and (3) allowing the water to react with thehydraulic cement to form crystalline hydration products, which hardensthe fresh concrete mixture to form the low-density hardened concrete.According to an embodiment of the invention, the at least one salt usedin this method may lead to enhanced initial penetration of the aqueoussolution into the pores and capillaries of the porous lightweightaggregate and helps retain water within the capillaries over time. Thesalt, according to an embodiment of the invention, may inhibit or slowdiffusion of water from the porous lightweight aggregate, therebycausing the hardened concrete to more quickly achieve a desired internalhumidity compared to hardened concrete made using the porous lightweightaggregate in the absence of the at least one salt. Slow release of waterover time may promote internal curing of the cementitious binder,particularly at low water-to-cement ratios, thereby increasing strengthand durability over time, according to certain embodiments of theinvention.

An aspect of the invention provides a concrete manufactured according tothe methods provided herein. In an embodiment of the invention, aconcrete formed from a cementitious composition or cementitious mixturehaving a lightweight aggregate treated with water-soluble solutions asprovided herein may result in: (1) high or nearly complete saturation ofthe pores and capillaries of lightweight aggregates with water duringtreatment, (2) prolonged water retention by the treated porousaggregates to better survive and prevent premature drying duringshipment and storage, (3) improved workability of freshly mixed concretesince the infused aggregates will absorb little, if any, of the wateradded during mixing to provide desired workability, (4) limiting releaseof water and/or water vapor from the porous aggregates during and afterhardening of the concrete structure, thereby enabling low-densityconcrete to attain and maintain a desired level of internal relativehumidity (e.g., 75% or below) within a shorter period of time, and (5)slow release of water from the porous aggregates over time after theconcrete has reached a desired level of internal relative humidity topromote “internal curing” of the cement binder over time, which canincrease concrete strength, particularly in low water-to-cement ratioconcrete.

In other embodiments of the invention, the water vapor attenuation agentmay comprise a water soluble salt. In certain preferred embodiments ofthe invention, the inorganic salt includes one or more of an alkalimetal halide salt. For example, the alkali metal halide salt may be anyof a sodium halide, a potassium halide, a lithium halide, and anycombination thereof. In preferred embodiments of the invention, thehalide group may be represented by a chloride or a bromide. Indeed anycombination of alkali metal chloride salts and alkali metal bromidesalts may be included in the cementitious composition.

In an embodiment of the invention, the cementitious compositioncomprises an alkali metal nitrite salt. In certain embodiments of theinvention, the cementitious composition comprises any combination of theaforementioned salts further combined with the alkali metal nitritesalt. In certain preferred embodiments, the ratio of alkali metal halidesalts to alkali metal nitrite salts is such that the halide and nitriteion concentration is substantially the same in the cementitious mix. Inother embodiments of the invention, the inorganic salt itself may be analkali metal nitrite salt, an alkali metal nitrate salt, and anycombination thereof. Pursuant to these aforementioned embodiments, thealkali metal nitrite salt may be a sodium nitrite.

In certain embodiments of the invention, the halide group may besubstituted by a pseudo halogen, such as a thiocyanate. Theconcentration of alkali metal halide salts in the cementitious mix,expressed based on a sodium chloride equivalent, may be in a range offrom about 0.2 wt % to about 4 wt %, preferably, from about 0.5 wt % toabout 2.5 wt %. For example, if sodium nitrite were to be used as thehumidity reducer in the cementitious composition, its concentrationwould be in a range of from about 0.24 wt % to about 4.72 wt %,preferably, from about 0.59 wt % to about 2.95 wt %—i.e., theconcentrations based on sodium chloride expressed above multiplied bythe molecular weight of sodium nitrite and divided by the molecularweight of sodium chloride. In certain embodiments of the invention, thesodium nitrite has a concentration at most about 7.5 wt %. In certainother preferred embodiments of the invention, the concentration ofsodium nitrite is from about 1.0 wt % to about 7.5 wt %. In yet certainother embodiments of the invention, the cementitious compositioncomprises at least one of an alkali metal halide salt, an alkali metalnitrate salt, and an alkali metal nitrite salt having a concentration offrom about 1.0 wt % to about 7.5 wt %. In still certain otherembodiments of the invention, the cementitious composition comprises atleast one of a sodium nitrite having a concentration of from about 1.0wt % to about 7.5 wt %.

In certain embodiments of the invention, the inventors have discoveredthat the mass-based presence of an alkali metal halide salt may be morepreferred especially since the mass of the remaining cementitious mixmay be influenced by the other compounds and their varying densities.For example, according to an embodiment of the invention, an amount ofalkali metal salt (e.g., sodium nitrite) in the cementitious mix may befrom about 5 pounds per cubic yard (“pcy”) to about 60 pcy. In otherembodiments of the invention, the amount of alkali metal halide salts inthe cementitious mix may be from about 10 pcy to about 50 pcy. In stillother embodiments of the invention, the amount of alkali metal halidesalts in the cementitious mix may be from about 20 pcy to about 40 pcy.

As discussed above, an appropriate concentration range of alkali metalsalt can normalized relative to molecular weight. Thus, forconcentrations or concentration range endpoints that are based on theweight of sodium nitrate as the standard, a normalize concentration orconcentration range endpoint for any other alkali metal salt can bedetermined according to Equation (III):

Weight (NaNO₂)×(MW Salt/ions per mole÷69/ions per mole)=EquivalentWeight Salt   Equation (III).

For binary salts, Equation (II) can be used:

Weight (NaNO₂)×(MW Salt÷69)=Equivalent Weight Salt   Equation (II).

Thus, exemplary concentration ranges for a binary alkali metal salt ofmolecular weight=X can be expressed as follows: about (X/69)5 pcy toabout (X/69)60 pcy, or about (X/69)10 pcy to about (X/69)50 pcy, orabout (X/69)20 pcy to about (X/69)40 pcy.

In some embodiments, the amount of alkali metal salt may vary dependingupon the type of cement used in the cementitious mix. In otherembodiments, the amount of alkali metal salt may vary depending upon thetypes of compounds and even perhaps their concentrations in thecementitious mix. Having the benefit of this disclosure, drying curvesmay be developed by a person having ordinary skill in the art, similarto those shown in FIGS. 9-11, for example, which are discussed in moredetail in the examples, to determine an appropriate amount of alkalimetal salt to yield concrete having an IRH of about 75-80% within aspecified time period or range.

By way of example, but without intending to be limiting, the dryingcurve of FIG. 9 shows that an appropriate amount of sodium nitrite forthat given cementitious mix is about 20 lb/yd³. On the other hand, thedrying curve of FIG. 10 shows that for another type of cement, which isdifferent than the cement used in the samples of FIG. 9, the anappropriate amount of sodium nitrite for that cementitious mix is about30 lb/yd³ or maybe up to 40 lb/yd³ depending upon the preferred surfacedrying characteristics to be achieved over time.

As further illustrated by the samples in FIG. 8, the presence of anothercompound of the invention may be used to reduce the amount of any of analkali metal halide salt; at least one of an alkali metal halide salt,an alkali metal nitrate salt, and an alkali metal nitrite salt; orsodium nitrite in the cementitious mix. For example, the use of 15% byweight of silica fume in the cementitious mix may reduce the amount ofsodium nitrite used in the cementitious mix from about 30 lb/yd³ toabout 20 lb/yd³.

The cementitious compositions of the invention may be formulated by aproper selection of any combination of a cement; a binder and/or filler,including any pozzolan; an adjuvant and/or an additive; an aggregate;and a water vapor attenuation agent, as disclosed herein. Thecementitious compositions of the various embodiments of the inventionmay comprise a superplasticizer, even more preferably, a polycarboxylatesuperplasticizer.

In an embodiment of the invention, the cementitious composition includesa cement. In certain embodiments of the invention, the cement is anyhydraulic cement. Non-limiting examples of hydraulic cements suitablefor use in certain cementitious compositions of the invention includeany class of Portland cement; masonry cement; alumina cement; refractorycement; magnesia cements, such as magnesium phosphate cement andmagnesium potassium phosphate cement; calcium-based cements, such ascalcium aluminate cement, calcium sulfoaluminate cement, and calciumsulfate hemihydrate cement; natural cement; hydraulic hydrated lime; anycomplex derivative thereof; and any combination thereof.

Aggregates useful in the cementitious compositions of the inventioninclude, but are not limited to, sand, stone, gravel, and anycombination thereof. Aggregates may be further classified as coarseaggregates that include, for example, gravel, crushed stone, or ironblast furnace slag, and fine aggregates, which typically include a sand.As non-limiting examples, stone can include limestone, granite,sandstone, brownstone, river rock, conglomerate, calcite, dolomite,serpentine, travertine, slate, bluestone, gneiss, quarizitic sandstone,quartizite, and any combination thereof.

Other specialty aggregates include heavyweight aggregates andlightweight aggregates. Heavyweight aggregates can include, but are notlimited to, barite, magnetite, limonite, ilmenite, iron, and steel.

Common lightweight aggregates that are found in certain embodiments ofthe invention include, but are not limited to, slag, fly ash, silica,shale, diatomonous shale, expanded slate, sintered clay, perlite,vermiculite, and cinders. In certain embodiments of the invention,insulating aggregates may also be used. Non-limiting examples ofinsulating aggregates include pumice, perlite, vermiculite, scoria, anddiatomite. In yet other embodiments of the invention, the cementitiouscomposition may additionally comprise any of the aggregates selectedfrom expanded shale, expanded slate, expanded clay, expanded slag, fumedsilica, pelletized aggregate, processed fly ash, tuff, and macrolite. Instill other embodiments of the invention, an aggregate may comprise amasonry aggregate non-limiting examples of which include shale, clay,slate, expanded blast furnace slag, sintered fly ash, coal cinders,pumice, and scoria.

In certain embodiments of the invention, an aggregate may comprise anycombination of coarse aggregates and fine aggregates. Coarse aggregatesare generally considered those aggregate materials retained on a number4 sieve. Fine aggregates are generally considered those aggregatematerials that pass through the number 4 sieve. For example, refer toASTM C33 (2007), which supersedes ASTM C33 (2003), and ASTM C125 (2007),which supersedes ASTM C125 (2002) and ASTM C125 (2000a) standardspecifications for concrete additives for a more comprehensivedescription of how to distinguish between fine aggregates and coarseaggregates.

The cementitious compositions may comprise a cement replacement. Inpreferred embodiments of the invention, the cement replacement comprisesa finely divided material, preferably, the finely a finely dividedpozzolan and/or slag whose particle size is less than about 75 microns,and a finely divided highly reactive pozzolan whose particle size isless than about 75 microns. In other embodiments of the invention, thefinely divided material comprises a pozzolan, which, without intendingto be limiting, reacts with water and the lime released from cementhydration to form densifying calcium silicates. In certain embodimentsof the invention, the pozzolan may comprise any natural pozzolan; anyartificial pozzolan, such as, for example, a fly ash; and anycombination thereof. In yet other embodiments of the invention, thefinely divided material comprises a ground slag, preferably, a groundgranulated blast furnace slag.

In an embodiment of the invention, the cementitious compositioncomprises a cement replacement. In an embodiment of the invention, thecementitious composition comprises a cement replacement, the cementreplacement comprising a finely divided material.

In an embodiment of the invention, the cement replacement may comprise adensifying precursor. As used herein, the term “precursor” refers to acompound, complex or the like that, after at least one of becomingchemically activated, becoming hydrated, or through at least one otherpreparation step becomes converted into a desired form to serve tofurther densify a concrete. In certain embodiments of the invention, thedensifying precursor is a densifying calcium silicate precursor.

In an embodiment of the invention, the finely divided material comprisesa pozzolan and/or a slag. In a preferred embodiment of the invention,the pozzolan and/or the slag have a particle size of less than about 75microns. In another preferred embodiment of the invention, the pozzolanand/or slag have a particle size of less than about 45 microns. In anembodiment of the invention, the finely divided material comprises anyof a pozzolan, such as, for example, a fly ash; a hydraulic addition,such as, for example, a ground granulated blast furnace slag; and anycombination thereof, and the cementitious composition has a ratio byweight of finely divided material to total weight of the cementitiouscomposition of from about 0.05 to about 0.8, from about 0.20 to about0.80, and, preferably, from about 0.13 to about 0.75. In anotherembodiment of the invention, the finely divided material comprises ahighly reactive pozzolan and the cementitious composition has a ratio byweight of finely divided material to total weight of the cementitiouscomposition, preferably, from about 0.05 to about 0.2, and, morepreferably, from about 0.06 to about 0.10. In certain embodiments of theinvention, the finely divided material comprises a pozzolan selectedfrom the group consisting of any natural pozzolan; any artificialpozzolan, such as, for example, a fly ash; and any combination thereof.

In certain embodiments of the invention, the cementitious compositionincludes an admixture and/or additive including such admixtures oradditives that function as accelerators, shrinkage reducing agentsretarders, thickeners, tracers, air-entraining agents, air detrainingagents, corrosion inhibitors, pigments, wetting agents, antifoamingand/or defoaming agents, any polymer that is water soluble, waterrepellants, fibers, damp proofing agents, gas formers, permeabilityreducers, pumping aids, viscosity control additives, other rheologymodifying additives, fungicidal and/or germicidal agents, insecticidalagents, finely divided mineral admixtures, alkali-reactivity reducers,pH control agents and/or buffers, bonding admixtures, strength enhancingagents, shrinkage reduction agents, water reduction additives, and anymixture thereof.

In an embodiment of the invention, in addition to the water vaporattenuation agent, as further described herein, the cementitiouscomposition comprises a cement, preferably, a hydraulic cement, having aconcentration from about 10 wt % to about 80 wt %, and from about 25 wt% to about 70 wt % based on the total weight of the cementitiouscomposition. In certain embodiments of the invention, the cementitiouscomposition comprises a cement, preferably, a hydraulic cement, having aconcentration from about 8 wt % to about 35 wt %, from about 10 wt % toabout 30 wt %, from about 12 wt % to about 25 wt %, and from about 14 wt% to about 21 wt % based on the total weight of the cementitiouscomposition.

In certain embodiments of the invention, the cementitious compositionmay additionally comprise, at least one of any aggregate, a pozzolan,and any combination thereof.

Cementitious compositions of the invention may comprise porous ornon-porous lightweight aggregates or admixture to reduce the density andweight of concretes formed therefrom. Porous lightweight aggregates arereadily available from natural sources and are inexpensive to procure,manufacture and process. Examples of porous light-weight aggregatesinclude, but are not limited to, slag, shale, clay, slate, expandedslag, expanded shale, expanded clay, expanded slate, expanded slag,cinders, scoria, pumice, tuff, perlite, and vermiculite.

The porous lightweight aggregate, in an embodiment of the invention, maybe either structural aggregates having compression strength greater than2500 psi, or nonstructural aggregates having compression strength of2500 psi or less. Examples of structural lightweight aggregates includeshale, clay or slate expanded by rotary kiln or sintering; cinders; andexpanded slag. Examples of non-structural lightweight porous aggregatesinclude scoria, pumice, perlite and vermiculite.

In an embodiment of the invention, the cementitious compositioncomprises a fine aggregate having a concentration from about 50 wt % toabout 85 wt %, from about 60 wt % to about 80 wt %, and from about 65 wt% to about 75 wt % based on the total weight of the cementitiouscomposition. In another embodiment of the invention, the aggregatecomprises at least one fine aggregate and at least one coarse aggregatehaving a weight ratio of fine aggregate to total aggregate of from about0.25 to about 1.00, from about 0.30 to about 0.75, from about 0.35 toabout 0.65, from about 0.40 to about 0.55, and from about 0.40 to about0.50. In certain embodiments of the invention, the fine aggregate may bea porous lightweight aggregate.

The water retention of cement paste and/or lightweight aggregate andwater-vapor emission of concrete may be affected by salts dissolved insolutions filling the pores of the aggregates and/or by salts directlyadded to cement paste, according to certain embodiments of theinvention. Salts that form hydrates when exposed to water are preferred,as larger hydrate salts can be deposited in fine pores and aid inimpeding water movement from cement paste and/or aggregates. The use oflow water-cementitious material (w/cm) ratios, which enhance mortardesiccation rate, will leave substantial amounts of materialunder-hydrated. Moisture from lightweight particles, as opposed to thepressurized water outflow into the plastic concrete as free water, inlower w/cm ratio concretes (<0.45), may create an area of morecompletely hydrated material in the interfacial zone. A lowerpermeability may result, encapsulating some of the moisture within thelightweight aggregate particle itself, thereby further preventing watervapor movement into the surrounding mortar.

In certain embodiments of the invention, the cementitious compositioncomprises a pozzolan, such as, for example, a fly ash; a groundgranulated blast furnace slag GGBFS; and any combination thereof.Relative to the overall cementitious composition, the pozzolan can havea concentration from about 5 wt % to about 30 wt %, from about 6 wt % toabout 25 wt %, from about 7 wt % to about 20 wt %, and from about 13 wt% to about 17 wt % based on the total weight of the cementitiouscomposition exclusive of water. The concentration of GGBFS can be in arange of about 3% to about 16% by weight of the cementitious compositionexclusive of water and about 13.5% to about 73% by total weight ofcementitious binder. The concentration of fly ash can be in a range ofabout 1.3% to about 8% by weight of the cementitious compositionexclusive of water and about 5.9% to about 36.5% by total weight ofcementitious binder.

In other embodiments of the invention, the cementitious compositioncomprises a highly reactive pozzolan, such as, for example, metakaolin,silica fume, and the like, including any combinations thereof, having aconcentration from about 0.1 wt % to about 3 wt %, 0.5 wt % to about 2.5wt %, and from about 1.0 wt % to about 2.0 wt % based on the totalweight of the cementitious composition exclusive of water and about 4%to about 15% by total weight of cementitious binder.

In certain embodiments of the invention, a material selected from thegroup consisting of a pozzolan, a ground granulated blast furnace slag,and any combination thereof can be a very fine particulate material thatreduces the voidage in the cementitious composition resulting in animproved moisture resistance of the finished concrete.

In other embodiments, the inventive cementitious composition comprises adispersant. A non-limiting example of a dispersant includes anypolycarboxylate dispersant, with or without polyether units.Polycarboxylate dispersants include those disclosed in U.S. Pat. Publ.No. 2008/0156225 to Bury, entitled “Rheology Modifying Additive forCementitious Compositions,” fully incorporated herein by reference.Dispersants may additionally include chemicals that function as any oneof a plasticizer, a water reducer, a high range water reducer, afluidizer, an antiflocculating agent, or a superplasticizer. Exemplarysuperplasticizers are disclosed in U.S. Pat. Publ. No. 2008/0087199 toGartner, entitled “Cement Shrinkage Reducing Agent and Method forObtaining Cement Based Articles Having Reduced Shrinkage,” fullyincorporated herein by reference. Dispersants may be selected thatfunction as a superplasticizer.

In an embodiment of the invention, the cementitious composition furthercomprises a superplasticizer. Any superplasticizer disclosed herein orotherwise known in the art may be used in the cementitious compositionsof various embodiments of the invention. In a preferred embodiment ofthe invention, the superplasticizer comprises a polycarboxylateadmixture. A non-limiting example of a commercially availablepolycarboxylate superplasticizer includes GLENIUM® 3000 available fromBASF Corporation. GLENIUM 3000 comprises a polymer with a carbonbackbone having pendant side chains with the characteristic that atleast a portion of the side chains are attached to the carbon backbonethrough a carboxyl group or an ether group. GLENIUM 3000 is a liquid atambient conditions having a specific gravity of approximately 1.08.

For example, using a cementitious mix of 658 lb/yd³ of Type III cement,slump of 6 inches, air content of 5-6%, concrete temperature of 65° F.,and curing temperature of 65 ° F., it has been reported that GLENIUM3000 provides a greater than 2 times increase in compressive strength inconcrete after 8 hours of curing and an improvement of approximately 30%after 12 hours of curing compared to that of a conventionalsuperplasticizer. For a cementitious mix of 658 lb/yd³ of Type I cement,slump of 8-9 inches, non-air-entrained, concrete temperature of 70° F.,dosage of admixtures adjusted to obtain 30% water reduction, GLENIUM3000 has been shown to reduce the initial set time by as much as 2 hoursand 33 minutes compared to that of a conventional superplasticizer.

In an embodiment of the invention, the superplasticizer is in the formof a liquid. In certain embodiments of the invention, the amount ofsuperplasticizer added to the cementitious composition is from about 2ounces to about 30 ounces, from about 4 ounces to about 24 ounces, fromabout 4 ounces to about 20 ounces, and from about 8 ounces to about 20ounces for every 100 pounds of cementitious composition. In certainpreferred embodiments of the invention, the superplasticizer added tothe cementitious composition is from about 4 ounces to about 16 ounces,more preferably, about 5 ounces to about 8 ounces, and, even morepreferably, about 8 ounces for every 100 pounds of cementitiouscomposition.

In an embodiment of the invention, the cementitious composition maycomprise a water reducer. A non-limiting example of a water reduceradmixture includes POLYHEED® 997, an ASTM C494 type A water reducer,supplied by BASF Corporation. In certain embodiments of the invention,it is more preferred to use a water reducer with a superplasticizer inorder to achieve a greater reduction in the amount of water mixed withthe cementitious composition.

In an embodiment of the invention, the cementitious composition mayadditionally comprise prepuff particles such as those disclosed in U.S.Pat. Publ. No. 2008/0058446 to Guevare et al., entitled “LightweightConcrete Compositions,” fully incorporated herein by reference. In anexemplary embodiment, the prepuff particles are polymer particles havingan average particle size of at least about 0.2 mm, at least about 0.3mm, at least about 0.5 mm, at least about 0.9 mm, and at least about 1mm up to at most about 8 mm, at most about 6 mm, at most about 5 mm, atmost about 4 mm, at most about 3 mm, and at most about 2.5 mm.

As disclosed herein, the cementitious composition is combined withwater, which functions as chemical water or hydration water and asexcess water that, among other things, serves to plasticize thecementitious mix to render it more flowable. In some embodiments, theexcess water, otherwise known as water of convenience, can be minimized.Alternatively, water vapor attenuation agents are selected to consume orscavenge certain amounts of the water of convenience. In yet otherembodiments, the water of convenience is both minimized and consumed orscavenged based on the use of certain one or more water vaporattenuation agents.

While it is well-known in the art to include additives such as aplasticizer, more preferably, a superplasticizer, in order to reduce theamount of water of convenience needed, conventionally, the dependence onexcess water has not been entirely eliminated. For example, conventionalcement mixtures tend to have water to cementitious ratios on the orderof 0.4 or higher. Specialty formulations that include a superplasticizerhave been disclosed that reduce the water to cementitious ratio to 0.25or higher, for example, similar to those compositions disclosed in U.S.Pat. No. 6,858,074 to Anderson et al., entitled “High Early-StrengthCementitious Composition.”

In certain embodiments, the cementitious compositions are combined withwater having a water to cementitious ratio of less that about 0.7, lessthan about 0.6, less than about 0.5, less than about 0.4, less thanabout 0.35, less than about 0.3, and less than about 0.25. In certainembodiments of the invention, the cementitious compositions are mixedwith water in a water to cementitious ratio of about 0.2 or higher. Inpreferred embodiments of the invention, the cementitious compositionsare mixed with water in a water to cementitious ratio of from about 0.2to about 0.6. Based on knowledge prior to the information provided inthis disclosure, a person having ordinary skill in the art would havebeen motivated merely to minimize, within certain limits, depending onother factors, the water to cementitious ratio of the cementitious mix.However, as this disclosure teaches, the inventive cementitiouscompositions may be formulated with one or more water vapor attenuationagents that allow higher water to cementitious ratios while stillattenuating or decreasing the rate of water vapor emissions in thecementitious mix.

Another aspect of the invention provides methods of preparingcementitious compositions. In a preferred embodiment of the invention, acementitious composition prepared according to certain embodiments ofthe invention is used to further prepare a concrete having an attenuatedor decreased rate of water vapor emission after curing or hardening. Ina preferred embodiment of the invention, the cementitious composition isproportioned to achieve rapid drying, which can be measured, forexample, by the ASTM test procedures for vapor emissions or internalrelative humidity, as described herein. In certain other embodiments ofthe invention, the cementitious composition is proportioned to achieve adesired property of a hardened concrete, which preferably can bemeasured using any of the various inventive procedures defined herein.

In an embodiment of the invention, a method for preparing a cementitiouscomposition comprises the steps of mixing a hydraulic cement with awater vapor attenuation agent that may include any of an ultrafinecalcium carbonate, preferably, having an average particle size of lessthan or equal to about 3 microns; a highly reactive pozzolan,preferably, silica fume and, more preferably, metakaolin; a shrinkagereducing agent, preferably, any one of polypropylene glycol, anycopolymer thereof, any derivative thereof, and any combination thereof;a humidity reducer, preferably, an alkali metal halide salt, an alkalimetal pseudo halide salt, an alkali metal nitrate salt, an alkali metalnitrate salt, preferably, sodium nitrite, sodium formate, sodiumacetate, and any combination thereof; and combinations thereof. In anembodiment of the invention, the water vapor attenuation agent has aconcentration between about 0.5% to about 18% by weight based on a totalweight of cementitious compounds. In a preferred embodiment of theinvention, the cementitious composition will be used to form acementitious mix that produces a concrete having an attenuated watervapor emission rate of between about 3 lb/1000 ft²/24 h to about 5lb/1000 ft²/24 h in less than or equal to about 30 days, less than orequal to about 25 days, less than or equal to about 21 days, less thanor equal to about 18 days, preferably, less than or equal to about 15days, more preferably, less than or equal to about 12 days, and, evenmore preferably, less than or equal to about 10 days after hardening.

In an embodiment of the invention, the method for preparing thecementitious composition may additionally include the step of adding acement replacement. The cement replacement may comprise a finely dividedmaterial. In an embodiment of the invention, the finely divided materialhas a particle size of less than about 75 microns. For example, a finelydivided material having a particle size of less than about 75 micronsmay be the material retained on a standard sieve having 75 micronopenings. Alternatively, a finely divided material having a particlesize of less than about 75 microns may be the material that passesthrough a standard sieve having a varying plurality of openings of +/−75micron. In another embodiment of the invention, the finely dividedmaterial has a particle size of less than about 45 microns. In yetanother embodiment of the invention, the finely divided materialcomprises a material that passes through a standard sieve size of 200.

In another embodiment of the invention, the finely divided material isselected from the group consisting of a pozzolan, such as, for example,a fly ash; a ground granulated blast furnace slag; and any combinationthereof. Further to this embodiment, the cementitious composition has aratio by weight of finely divided material to total weight of thecementitious composition of from about 0.03 to about 0.8, and,alternatively, from about 0.15 to about 0.8.

In still another embodiment of the invention, the finely dividedmaterial comprises a highly reactive pozzolan selected from the groupconsisting of silica fume, metakaolin, and any combination thereof.Further to this embodiment, the cementitious composition has a ratio byweight of finely divided material to cement of from about 0.05 to about0.20.

In certain embodiments of the invention, the cement replacementcomprises a densifying precursor. In a preferred embodiment of theinvention, the densifying precursor is a densifying calcium silicateprecursor.

In an embodiment of the invention, the method for preparing acementitious composition includes the step of including asuperplasticizer. The superplasticizer has a concentration in a rangefrom about 1 ounce to about 6 ounces for every 100 pounds of the totalweight of the cementitious composition. In a preferred embodiment of theinvention, the superplasticizer includes a polycarboxylatesuperplasticizer.

In an embodiment of the invention, the method for preparing acementitious composition additionally comprises the step ofincorporating an aggregate in the cementitious composition. In anembodiment of the invention, the aggregate comprises at least one of afine aggregate, a course aggregate, and combinations thereof.

Another aspect of the invention provides a method for the treatment ofporous aggregates used certain cementitious compositions or concretecompositions of the invention. In an embodiment of the invention,treatment of porous aggregates comprises heating the aggregates andquenching the hot aggregates with a solution of one or more salts. Inalternative embodiments of the invention, porous aggregates may besoaked in solutions without first heating the aggregates. In otherembodiments of the invention, the soaked aggregates may be boiled in thesolution. In certain embodiments of the invention the solution of one ormore salts is an aqueous solution. In certain embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 1% by weight to about 20% by weight base on atotal weight of the solution. In certain other embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 5% by weight to about 20% by weight base on atotal weight of the solution. In yet certain other embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 5% by weight to about 15% by weight base on atotal weight of the solution. In still certain other embodiments of theinvention, the concentration of the one or more salts in the solution isin a range of from about 8% by weight to about 20% by weight base on atotal weight of the solution.

In embodiments of the invention when the aggregates are heated beforequenching by the solution, they can be heated to a temperature higherthan 200° F., more preferably higher than 250° F., and more preferablyin the range of 300-400° F. An example embodiment of the soaking orquenching solution is a solution of sodium acetate in a concentration of1 to 2.5 mol/L. Without intending to be bound by theory, lightweightaggregates treated in this fashion may have extended moisture retention,and the resulting low-density concrete may have an accelerated speed toreach 75% internal relative humidity, improved internal curing and otherenhanced concrete characteristics. In an embodiment of the invention, aprocess for treating porous aggregates used in certain cementitiouscompositions of the invention utilizes hot finished and sized product orlightweight clinker, and quenches and cools the aggregate in an aqueouschemical bath so that a substantial amount of the capillaries of thelightweight become filled with solution. The preferred lightweight orclinker temperature is about 350° F. (177° C.). The steam, initiallyquench generated, may be forced into the smaller capillaries where itcondenses and fills the smaller capillaries with water. The solute maybecome dispersed through much of this system, increasing the water vaporretention by lowering the vapor pressure and modifying the water in themicro pores (less than 0.01 mm) and in mid-range pores as relativelynon-evaporable water. Because smaller pores in many lightweights mayconstitute a substantial amount of the total void system, thissequestered water is infused through certain methods of the inventioncan measurably impact the amount available to the mortar system asself-desiccation and atmospheric vapor emissions decrease the internalrelative concrete humidity to the desired 75% range.

In certain embodiments of the invention, salts may be directly attachedto outer surfaces of aggregates (e.g., to improve hydration of thebinder). For instance, certain chemicals or vectors that effect changein the concrete as a consequence of their dissolution into the paste maybe attached to the lightweight aggregate by allowing a short surfacedrying time and then applying the appropriate solution to the aggregateor leaving the soak or quench solution on the surface to evaporate anddeposit its solute. In one embodiment, an example solution to achievethis result comprises 15 wt % NaAc and 5 wt % NaCl.

An aspect of the invention provides porous lightweight aggregatestreated with salt for improved water saturation and water retentionmanufactured. Without intending to be bound by theory, the salt isintended to enhance penetration of aqueous solution into pores andcapillaries of the porous lightweight aggregate and helps retain waterwithin the capillaries over time, as compared to porous lightweightaggregate treated with only water without the salt. Small pores of thelightweight aggregates may be filled with solutions to higher levelsthan typically achievable with the conventional use of water alone. Thesolution-filled aggregates of the invention may retain water in thepores for prolonged periods and may facilitate rewetting of largerpores. According to certain embodiments of the invention, higher levelsof water saturation of the lightweight aggregates may prevent absorptionof water when using a concrete pump, avoiding loss of workability orplasticity. Moreover, such treated porous aggregates yield concrete withlower internal humidity.

Another aspect of the various embodiments of the invention provides acementitious mix comprising any of the cementitious compositions of theinvention. In certain embodiments of the invention, the cementitious mixcomprises an amount of water sufficient to provide a water tocementitious ratio of from about 0.05 to about 0.7; from about 0.1 toabout 0.6; preferably, from about 0.2 to about 0.5; and, morepreferably, from about 0.25 to about 0.4.

In certain embodiments of the invention, the cementitious mix comprisesa hydraulic cement, an aggregate, a cement replacement, a water vaporattenuation agent, water, and a superplasticizer. In a preferredembodiment of the invention, the cement replacement is a densifyingcalcium silicate precursor. In another preferred embodiment of theinvention, the superplasticizer is a polycarboxylate superplasticizer.

According to certain embodiments of the invention, the cementitious mixcomprises a hydraulic cement having a concentration from about 8 wt % toabout 35 wt % based on a total weight of cementitious compounds; anaggregate having a concentration from about 25 wt % to about 85 wt %based on the total weight of cementitious compounds; a densifyingcalcium silicate precursor having a concentration from about 3 wt % toabout 80 wt % based on the total weight of cementitious compounds; awater vapor attenuation agent having a concentration from about 0.5 wt %to about 18 wt % based on the total weight of cementitious compounds; anamount of water sufficient to provide a water to cementitious ratio offrom about 0.2 to about 0.4; and a polycarboxylate superplasticizerhaving a concentration from about 4 ounces to about 16 ounces per 100pounds of cementitious compounds.

In an exemplary embodiment of the invention, the cementitious mixcomprises a hydraulic cement having a concentration from about 8 wt % toabout 35 wt % based on a total weight of cementitious compounds; anaggregate having a concentration from about 25 wt % to about 85 wt %,preferably, from about 35 wt % to about 75 wt % based on the totalweight of cementitious compounds; a densifying calcium silicateprecursor having a concentration from about 3 wt % to about 80 wt %,preferably, from about 5 wt % to about 25 wt % based on the total weightof cementitious compounds; an amount of water sufficient to provide awater to cementitious ratio of from about 0.2 to about 0.6; and apolycarboxylate superplasticizer having a concentration from about 1ounce to about 6 ounces per 100 pounds of cementitious compounds.

An aspect of the invention provides methods of manufacturing freshlymixed concrete having improved workability and faster surface drying. Anembodiment of a method of the invention comprises: (1) adding a saltdirectly to the concrete mix and/or providing a porous lightweightaggregate infused with an aqueous solution comprising water and at leastone salt; (2) preparing a fresh concrete mixture by blending aggregate,hydraulic cement, salt and water; and (3) permitting the concrete toharden. Without intending to be bound by theory, the salt may enhanceretention of water within the cement paste capillaries and/or the poresof lightweight aggregate over time. A reduced IRH, hastened surfacedrying, and inhibition of autogenous and drying shrinkage may berealized in certain concrete mixes of the invention. The salt may alsoenhance wetting of the pores of a porous lightweight aggregates, whichmay result in an increased workability of the fresh concrete mixturewhen compared to a fresh concrete mixture conventionally made withoutusing the salt.

When using porous aggregates, relatively brief storage of such materialsin normal (50%) atmospheric relative humidity will rapidly desiccateparticles saturated only with plain water. In contrast, aggregatesinfused with aqueous salt solution of the invention loses water byevaporation at a slower rate and quickly rehydrates as large voidsrefill with water to a saturated condition upon contact with concretemix water. The need for additional mix water to compensate for pumppressure workability loss may also be minimized. Further, the concretemix can better accommodate the use of super-plasticizers since the lossof the more efficient plasticized mix water under the influence of pumppressure is minimized. Plasticizers can reduce water contents by 10% ormore, thereby speeding the internal drying process.

After the fresh concrete mixture exits the concrete pump, the saltprevents air-pressurized water from being released back to thenon-aggregate components of the concrete, which allows the freshconcrete to maintain desired workability and avoid problems associatedwith excess water, such as bleeding and segregation. Furthermore, thesalt inhibits or slows diffusion of water from the porous lightweightaggregate and cement paste, thereby causing the hardened concrete tomore quickly achieve a desired internal humidity (e.g., 75% or less)compared to hardened concrete made in the absence of the salt.

Furthermore, the water contained in pores of lightweight aggregates maybe gradually released and react with cementitious binder materials afterthe concrete reaches a desired internal relative humidity, which resultsin prolonged hydration and internal curing and a resulting increase inlong-term strength of the concrete manufactured using the cementitiouscompositions or according to certain methods of the invention.

When structural lightweight aggregates are used to make low-densityconcretes according to the disclosed inventive processes, the resultingconcrete would have density and compressive strength suitable forstructural application, with density in the range of 80-120 lb/ft³ (pcf)and compressive strength in the range of 2500-6000 psi. Whennon-structural lightweight aggregates are used, concretes are suitableas fill concrete or insulating concrete when the density is in the rangeof 50-90 pcf and compressive strength 1000-2000 psi; or as insulatingconcrete when density is smaller than 50 pcf and compressive strength isin the range of 300-1000 psi.

In an embodiment of the invention, a method for preparing a concretestructure using a cementitious composition comprises the steps of mixinga hydraulic cement and a water vapor attenuation agent; adding any of acement replacement, an admixture, and a superplasticizer; and blendingan amount of water into the cementitious composition to prepare acementitious mix. In a preferred embodiment of the invention, thecementitious mix will produce a hardened concrete having an attenuatedwater vapor emission rate of between about 3 lb/1000 ft²/24 h to about 5lb/1000 ft²/24 h in less than or equal to about 50 days, less than orequal to about 36 days, less than or equal to about 30 days, less thanor equal to about 28 days, less than or equal to about 25 days, lessthan or equal to about 21 days, less than or equal to about 18 days,preferably, less than or equal to about 15 days, more preferably, lessthan or equal to about 12 days, even more preferably, less than or equalto about 10 days, and, yet even more preferably, less than or equal toabout 7 days.

Generally, the method of using the cementitious composition additionallycomprises the steps of using the cementitious mix to form a cementitioussegment or a preform of the concrete structure and curing thecementitious segment or preform of the concrete structure to a hardenedconcrete. Further to this embodiment, the cementitious segment may besubjected to additional processing steps. For example, a trowel may beapplied to the cementitious segment to, for example, smooth the surfaceof the cementitious segment and/or to even the distribution of thecementitious mix in a form.

In certain embodiments of the invention, the methods of use mayadditionally comprise the step of applying a regimen and/or techniquethat facilitates a more rapid curing of the cementitious mix to ahardened concrete. Any technique known in the art may be used to morerapidly cure the cementitious mix. Non-limiting examples of suchtechniques include applying a moisture barrier between a moisture sourceand the formed cementitious segment; maintaining the movement of air atthe surface of the cementitious segment being cured to ensure water thatevolves from the segment is removed; heating, for example, with thermaland/or radiant heat, the cementitious segment being cured; andcontrolling humidity between the moisture barrier and the formedcementitious segment by the maintaining and heating steps.

In an embodiment of the invention, the water vapor attenuation agent mayinclude any of a highly reactive pozzolan, preferably, silica fume and,more preferably, metakaolin; a shrinkage reducing agent, preferably, anyone of polypropylene glycol, any copolymer thereof, any derivativethereof, and any combination thereof; an inorganic accelerator,preferably, an alkali metal halide salt, an alkali metal pseudo halidesalt, an alkali metal nitrate salt, an alkali metal nitrite salt,preferably, sodium nitrite, and any combination thereof; andcombinations thereof. In an embodiment of the invention, the water vaporattenuation agent has a concentration between about 0.5% to about 18% byweight based on a total weight of cementitious compounds.

In an embodiment of the invention, the cement replacement comprises afinely divided material. In certain embodiments of the invention, thefinely divided material has a particle size of less than about 75microns. In an embodiment of the invention, the finely divided materialis a material that passes through a standard sieve size of 200. Incertain embodiments of the invention, the finely divided materialcomprises a cement replacement.

In another embodiment of the invention, the finely divided material isselected from the group consisting of a pozzolan, such as, for example,a fly ash; a ground granulated blast furnace slag; and any combinationthereof. Further to this embodiment, the cementitious composition has aratio by weight of finely divided material to cement of from about 0.15to about 0.8.

In still another embodiment of the invention, the finely dividedmaterial comprises a highly reactive pozzolan selected from the groupconsisting of silica fume, metakaolin, and any combination thereof.Further to this embodiment, the cementitious composition has a ratio byweight of finely divided material to cement of from about 0.06 to about0.105.

In certain embodiments of the invention, the cement replacementcomprises a densifying precursor. In a preferred embodiment of theinvention, the densifying precursor is a densifying calcium silicateprecursor.

In an embodiment of the invention, the superplasticizer has aconcentration in a range from about 4 ounces to about 20 ounces forevery 100 pounds of cementitious composition. In a preferred embodimentof the invention, the superplasticizer at least includes apolycarboxylate superplasticizer.

In a preferred embodiment of the invention, the amount of water and aratio by weight of the water vapor attenuation agent to the hydrauliccement, which may encompass any of the other compounds as disclosedherein, are proportioned to hydrolyze the cementitious composition andallow the prepared cementitious mix to achieve a desired level ofplasticity. In another preferred embodiment of the invention, the amountof water and a ratio by weight of the water vapor attenuation agentand/or finely divided material to the hydraulic cement, which mayencompass any of the other compounds as disclosed herein, areproportioned to achieve a desired level of plasticity while achieving adesired property of the concrete. In certain embodiments, the desiredproperty of the concrete is any of minimizing an amount of time neededto achieve a water vapor emission of the concrete, minimizing an amountof time needed to achieve an internal relative humidity of the concrete,a reduced shrinkage of the concrete, and any combination thereof.Without intending to be limiting, a reduced shrinkage of the concretewill reduce the curling or warping of the concrete when used in flooringapplications and allow for better control of joint spacing betweenconcrete segments.

In an embodiment of the invention, the method for preparing acementitious composition additionally comprises the step ofincorporating an aggregate into the cementitious composition. In anembodiment of the invention, the aggregate comprises at least one of afine aggregate, a course aggregate, and any combination thereof.

The combination of steps for preparing a cementitious composition foruse in preparing a concrete structure may be varied depending upon thedesired application of the finished concrete structure. For example, inmany circumstances, a concrete structure used in flooring must assurethat a dry substrate is available allowing a coating and/or sealant tobe applied within a reasonable amount of time. While not intending to belimiting, the compositions and methods of the invention are suitable forsuch applications because they provide a relatively fast dryingcementitious mix with an attenuated or reduced water vapor emissionsafter cure. Typically, the cementitious mixes for such applications aretypically characterized by an appropriate mix of cementitiouscompounds—i.e., cement(s), slag(s), water vapor attenuation agent(s),and/or pozzolans—available to react with the residual water allowing thewater vapor emissions to be reduced to about 3 lb/1000 ft²/24 h and aninternal relative humidity of about 75% to be achieved in 45 days. Therule-of-thumb for more conventional compositions is 1 month for everyinch of concrete thickness (e.g., 5 months for a commonly used 5 inchconcrete structure).

Another aspect of the invention provides cementitious compositionsmanufactured using any of the aforementioned methods of the invention.Yet another aspect of the invention provides a concrete manufacturedusing any of the aforementioned methods of the invention.

As disclosed herein, the critical parameters for achieving a relativelyfast drying concrete using the cementitious compositions of theinventions and methods as disclosed herein include any of the water tocementitious ratio; employing a curing technique that is adequate toassure eventual water impermeability; type and amount of the one or morewater vapor attenuation agents included in the cementitious composition;optionally, the use of a sufficiently fine material to create a densemass; and any combination thereof.

As a person having ordinary skill in the art having the benefit of thisdisclosure would understand, care must be exercised in blending anypozzolan in order to control the heat of hydration, or else thermalcracking of the concrete could become problematic rendering, for themost part, the use of any pozzolan virtually ineffective. As a personhaving ordinary skill in the art having the benefit of this disclosurewould further understand, care must also be exercised in proportioningand compounding the cementitious mix. For example, a cementitious mixthat is too sticky will be difficult to pump and finish usingconventional techniques.

EXAMPLES Examples 1-2

The purpose of the tests in Example 1 were to demonstrate the effect ofthe concentration of a polycarboxylate superplasticizer and the use of awater reducer on the use of chemically bound water and the extent ofshrinkage realized by the concrete sample mixes of Table 9.

TABLE 9 Sample 1 Sample 2 Sample 3 Compound/Property Concrete MixPortland Cement, Type I-II, lb 800 517 611 Sand, ASTM C33, lb 1,3001,525 1,500 1 inch Stone, ASTM C33, lb 1,850 1,850 1,850 GLENIUM 3000,oz/100 lb cement 16.0 — 8.0 POLYHEED 997, oz/100 lb cement — 5.3 —Water, lb 225 290 228 water to cement ratio 0.28 0.56 0.37 Air Content,% 1.7 3.4 5.4 Density, lb/ft³ (pcf) 155 147 148 Yield, ft³/yd³ 26.9 28.128.1 Slump, inches >6.00 4.25 5.25

The data in Table 10 shows the shrinkage results for the concrete mixesof the examples. The specimens were tested according to the ASTM C157(2006) protocol. Each shrinkage sample was cured at 73° F. and 100%humidity for 24 hours, and followed by a curing step while immersed inwater for 7 days. Drying was conducted at 50% relative humidity and 73°F.

TABLE 10 Sample 1 Sample 2 Sample 3 Days Drying Shrinkage, % 14 0.01330.0193 0.0133 21 0.0203 0.0290 0.0183 28 0.0227 0.0343 0.0217 35 0.02430.0387 0.0230 42 0.0303 0.0487 0.0300 56 0.0350 0.0560 0.0353

The cementitious composition of sample 2, which uses a water reducerinstead of a polycarboxylate superplasticizer shows the greatest amountof shrinkage. The cementitious compositions of samples 1 and 3 show thatthe amount of shrinkage can be somewhat maintained with varyingconcentrations of cement in the composition by changing the proportionof superplasticizer to control the water.

The purpose of the test in Example 2 was to show that the need foradditional water with an increasing concentration of cement in acementitious composition can be offset by increasing the use of asuperplasticizer and also by increasing the concentration of thesuperplasticizer in the cementitious composition. As the sample mixesillustrated in Table 8 show, sample 3 has 94 lbs more concrete thansample 2, and yet has a much smaller demand for water as a result ofusing a superplasticizer versus that of using a water reducer. Sample 1contains 189 lbs more cement than sample 3 and yet has a lower water tocementitious ratio as are result of increasing the concentration ofsuperplasticizer in the cementitious composition.

Example 3

The purpose of the tests in Example 3 were to demonstrate the effect ofa polycarboxylate superplasticizer on the reduction in the amount oftime needed to achieve a desired rate of water vapor emissions using theconcrete sample mixes of Table 11.

TABLE 11 Sample 4 Sample 5 Sample 6 Compound/Property Concrete MixPortland Cement, Type I-II, lb 800 517 611 Sand, ASTM C33, lb 1,3001,525 1,500 1 inch Stone, ASTM C33, lb 1,850 1,850 1,850 GLENIUM 3000,oz/100 lb cement 16.0 — 8.0 POLYHEED 997, oz/100 lb cement 5.3 Water, lb225 281 228 water to cement ratio 0.28 0.54 0.37 Air Content, % 3.4 N/A5.6 Density, lb/ft³ (pcf) 155 146 147 Yield, ft³/yd³ 27.0 28.2 28.2Slump, inches >6.00 4.50 5.00

The curing data and number of days required to achieve a water vaporemission rate of 3 lb/1000 ft²/24 hr shown in Table 12 were obtained bycasting each of the samples in a 2 foot×2 foot×5′/2 inch deep panellined with polyethylene. Immediately prior to initial set, each panelwas given a steel trowel finish and sealed for the noted cure period at73° F. Following the cure period, the concrete slabs were unsealed andallowed to dry at 50% relative humidity and 73° F. in a drying room. Thewater vapor emissions data was obtained by averaging two calciumchloride dome tests conducted according to the ASTM F1869 test standard.

TABLE 12 Sample 4 Sample 5 Sample 6 Curing Time, days 28 28 28 DryingTime needed for 17 >50 22 3 lb/1000 ft² 24 hr Emissions, days

The mixture of sample 5 has a water to cementitious ratio that isgreater than that of samples 4 and 6; however, the sample requiresgreater than 50 days drying in order to achieve a water vapor emissionsrate of 3 lb/1000 ft²/24 hr. The mix of sample 6 shows asuperplasticizer helps to attenuate the water vapor emissions over thatof the water reducer used in the mix of sample 5. Sample 4 shows thatincreasing the concentration of the superplasticizer further reduces theamount of drying time needed to achieve the desired water vaporemissions rate.

Example 4

The purpose of the tests in Example 4 were to demonstrate the effect ofa polycarboxylate superplasticizer along with the presence of a reactivepozzolan on the amount of time needed to reduce the internal relativehumidity to a desired value using the concrete sample mixes of Table 13.

TABLE 13 Concrete Mix Compound/Property Sample 7 Sample 8 Sample 9Hanson Cement, Type I-II, lb 517 740 740 Silica Fume, lb — 60 —Metakaolin, lb — — 60 Sand, ASTM C33, lb 1,525 1,200 1,200 Sand, ASTMC33 #67, lb 1,950 1,950 1,950 GLENIUM 3000, oz/100 lb cement — 16.2 16.2POLYHEED 997, oz/100 lb cement 5.0 — — Colloid Defoamer, oz 0.5 0.5 0.5Water, lb 264 186 197 water to cement ratio 0.51 0.23 0.25 MixTemperature, ° F. 65 66 67 Air Content, % 1.3 3.6 1.1 Density, lb/ft³(pcf) 152 156 156 Yield, ft³/yds 28.1 26.5 26.7 Slump, inches 5.75flowing flowing

Each sample was cast in a 2 foot×2 foot×5½ inch deep panel lined withpolyethylene. Immediately prior to initial set, each panel was given asteel trowel finish and sealed for a 13-day cure period at 73° F.Following the cure period, the concrete slabs were unsealed and allowedto dry at 50% relative humidity and 73° F. in a drying room. Therelative humidity was obtained according to the ASTM F 2170 testprocedure using in situ probes. The curing data and number of daysrequired to achieve an internal relative humidity of 75% for the curedconcrete samples are shown in Table 14.

TABLE 14 Sample 7 Sample 8 Sample 9 Curing Time, days 13 13 13 DryingTime needed to Achieve >63 28 28 75% Relative Humidity, days

The cementitious composition of sample 7, which used only the waterreducer, produced a concrete having an internal relative humidity of87.3% at the end of 63 days. Samples 8 and 9 comprising silica fume andmetakaolin, respectively, as well as a superplasticizer produced aconcrete that required only 28 days of drying time to achieve aninternal relative humidity of 75%.

Example 5

The purpose of the tests in Example 5 was to demonstrate the effect ofpartial substitution with a finely divided material (finely dividedground granulated blast furnace slag and finely divided type F fly ash)generally smaller than a U.S. standard sieve size 200 or particleshaving a size less than about 75 microns along with a superplasticizerin the cementitious compositions using the sample mixes of Table 15.

TABLE 15 Concrete Mix Compound/ Sample Sample Sample Sample SampleProperty 14 15 16 17 18 Cement, lb 800 600 400 560 680 Ground Slag, lb —200 400 — — Fly Ash - Type — — — 240 120 F, lb Sand, lb 1,300 1,3001,300 1,300 1,300 GLENIUM 8 8 8 8 8 3000, oz/100 lb cement Water, lb 195190 190 210 198 water to cement 0.24 0.24 0.24 0.26 0.25 ratio Density,lb/ft³ 151 150 149 144 148 (pcf) Yield, cc³ 950 957 960 1006 971 Slump(Spread), flowing flowing flowing flowing flowing inches

The sample mixes were analyzed using the mortar method, as furtherdisclosed herein. Mortar of the same workability level as the concreteof the investigation was mixed and cast in 6 inch×6 inch plastic pans toa depth of 1⅝ inches. The samples were cured unsealed for 24 hours andthen sealed for a 14-day cure. Vapor loss measurements were determinedbased on the changes in weight of the samples and is reported in Table16.

TABLE 16 Sample Sample Sample Sample Sample 14 15 16 17 18 Total WaterVapor 3.7 2.9 4.4 7.4 5.6 Loss, gr

Increasing the amount of ground granulated blast furnace slag, as shownin samples 15 and 16, resulted in the same water to cementitious ratioand produced a vapor loss in the same range as sample 14, the controlmix. Substitution of type F fly ash in samples 17 and 18 resulted inprogressively higher vapor emissions over the curing period, butrepresent rates that still are within a satisfactory range.

Example 6

The sample mixes of Tables 17 and 18 were used to analyze the variationsin water loss measured from the 6 inch×6 inch mortar samples pans formixes comprising cements and sands from five different regions. Theaverage vapor loss for these samples was 6.34, while the standarddeviation for the sample was 1.08.

TABLE 17 Sample Sample Sample Sample Sample 19 20 21 22 23 Cement, grPermanente, CA 650 — — — — Maryland — 650 — — — Texas — — 650 — —Michigan — — — 650 — Tennessee — — — — 650 Sand, gr Seacheldt 1,4301,430 1,430 1,430 1,430 Maryland — — — — — Texas — — — — — Michigan — —— — — Tennessee — — — — — Glenium 3000, 16 16 16 16 16 oz/100 lb cementWater, gr 190 208 208 216 210 water to cement ratio 0.29 0.32 0.32 0.330.32 Density, lb/ft³ (pcf) 149 148 148 146 147 Yield, cc³ 953 968 967985 976 Slump, inches 8.0 6.3 6.0 5.5 5.5 Mix Temperature, ° F. 75.076.0 75.0 76.0 75.0 Vapor Loss, gr 8.0 6.3 6.0 5.5 5.5

TABLE 18 Sample Sample Sample Sample 24 25 26 27 Cement, gr Permanente,CA — — — — Maryland 650 — — — Texas — 650 — — Michigan — — 650 —Tennessee — — — 650 Sand, gr Seacheldt — — — — Maryland 1,430 — — —Texas — 1,430 — — Michigan — — 1,430 — Tennessee — — — 1,430 Glenium3000, oz/100 lb cement 35 16 16 16 Water, gr 224 204 216 206 water tocement ratio 0.34 0.32 0.33 0.32 Density, lb/ft³ (pcf) 144 148 146 149Yield, cc³ 1003 970 988 960 Slump, inches 5.0 8.0 5.5 7.3 MixTemperature, ° F. 75.0 76.0 75.0 75.0 Vapor Loss, gr 5.0 8.0 5.5 7.3

Examples 7-8

The purpose of the tests in Example 7 were to demonstrate the effect ofthe concentration of a polycarboxylate superplasticizer and the use of awater reducer on the use of chemically bound water and the extent ofshrinkage realized by the concrete sample mixes of Table 19.

TABLE 19 Concrete Mix Compound/Property Sample 28 Sample 29 Sample 30Portland Cement, Type I-II, lb 800 517 611 Sand, ASTM C33, lb 1,3001,525 1,500 1 inch Stone, ASTM C33, lb 1,850 1,850 1,850 GLENIUM 3000,oz/100 lb cement 16.0 — 8.0 POLYHEED 997, oz/100 lb cement — 5.3 —Water, lb 225 290 228 water to cement ratio 0.28 0.56 0.37 Air Content,% 1.7 3.4 5.4 Density, lb/ft³ (pcf) 155 147 148 Yield, ft³/yd³ 26.9 28.128.1 Slump, inches >6.00 4.25 5.25

The data in Table 20 shows the shrinkage results for the concrete mixesof the examples. The specimens were tested according to the ASTM C157(2006) protocol. Each sample was cured at 73° F. and 100% relativehumidity for 24 hours, and followed by a curing step while immersed inwater for 7 days. Drying was conducted at 50% relative humidity and 73°F.

TABLE 20 Shrinkage, % Days Drying Sample 28 Sample 29 Sample 30 140.0133 0.0193 0.0133 21 0.0203 0.0290 0.0183 28 0.0227 0.0343 0.0217 350.0243 0.0387 0.0230 42 0.0303 0.0487 0.0300 56 0.0350 0.0560 0.0353

The cementitious composition of sample 29, which uses a water reducerinstead of a polycarboxylate superplasticizer, shows the greatest amountof shrinkage. The cementitious compositions of samples 28 and 30 showthat the amount of shrinkage can be somewhat maintained with varyingconcentrations of cement in the composition by changing the proportionof superplasticizer to control the water.

The purpose of the test in Example 8 was to show that the need foradditional water with an increasing concentration of cement in acementitious composition can be offset by increasing the use of asuperplasticizer and also by increasing the concentration of thesuperplasticizer in the cementitious composition. As the sample mixesillustrated in Tables 19 and 20 show, sample 30 has 94 lbs more concretethan sample 29, and yet has a much smaller demand for water as a resultof using a superplasticizer versus using a water reducer. Sample 28contains 189 lbs more cement than sample 30 and yet has a lower water tocement ratio as a result of increasing the concentration ofsuperplasticizer in the cementitious composition.

Example 9

The purpose of the test in Example 9 was to demonstrate the effect of apolycarboxylate superplasticizer along with the presence of a reactivepozzolan on the amount of time needed to reduce the internal relativehumidity to a desired value using the concrete sample mixes of Table 21.

TABLE 21 Concrete Mix Compound/Property Sample 33 Sample 34 Sample 35Hanson Cement, Type I-II, lb 517 740 740 Silica Fume, lb — 60 —Metakaolin, lb — — 60 Sand, ASTM C33, lb 1,525 1,200 1,200 Sand, ASTMC33 #67, lb 1,950 1,950 1,950 GLENIUM 3000, oz/100 lb cement — 16.2 16.2POLYHEED 997, oz/100 lb cement 5.0 — — Colloid Defoamer, oz 0.5 0.5 0.5Water, lb 264 186 197 water to cement ratio 0.51 0.23 0.25 MixTemperature, ° F. 65 66 67 Air Content, % 1.3 3.6 1.1 Density, lb/ft³(pcf) 152 156 156 Yield, ft³/yd³ 28.1 26.5 26.7 Slump, inches 5.75flowing flowing

Each sample was cast in a 2 foot×2 foot×5½ inch deep panel lined withpolyethylene. Immediately prior to initial set, each panel was given asteel trowel finish and sealed for a 13-day cure period at 73° F.Following the cure period, the concrete slabs were unsealed and allowedto dry at 50% relative humidity and 73° F. in a drying room. Therelative humidity was obtained according to the ASTM F 2170 testprocedure using in situ probes. The curing data and number of daysrequired to achieve an internal relative humidity of 75% for the curedconcrete samples are shown in Table 22.

TABLE 22 Sample 33 Sample 34 Sample 35 Curing Time, days   13 13 13Drying Time needed to Achieve >63 28 28 75% Relative Humidity, days

The cementitious composition of sample 33, which used only the waterreducer, produced a concrete having an internal relative humidity of87.3% at the end of 63 days. Samples 34 and 35 comprising silica fumeand metakaolin, respectively, as well as a superplasticizer produced aconcrete that required only 28 days of drying time to achieve aninternal relative humidity of 75%.

Example 10

The purpose of the tests in Example 10 was to demonstrate the effect ofan inorganic accelerator on the reduction in relative humidity for thecementitious compositions using the sample mixes of Table 23.

TABLE 23 Concrete Mix Compound/Property Sample 40 Sample 41 Sample 42cement, lb/yard balance balance balance sodium chloride, lb/yard  0 1120 water to cement ratio same same same days to 75% relative humidity 2919 17

As shown by samples 41 and 42 over control sample 40, concrete mixturescomprising sodium chlorides as an inorganic accelerator, indeed, evenincreasing amounts of the use of the sodium chloride, show a reductionin the amount of time needed to achieve a 75% relative humidity.

Example 11

The purpose of the tests in Example 11 was to demonstrate theimprovement in water retention of lightweight aggregates treated withthe various aqueous solutions. In Example 11, lightweight aggregateswere heated, quenched, air dried, and re-immersed in water or solutions.Lightweight aggregates of 3/8 inch average diameter were heated to 350°F., then quenched in 7 different chemical solutions in Samples 44-50,which were aqueous solutions containing one of NaNO₃, NaNO₂, K₂CO₃,NaAc, Na2SO4, K₂SO₄ and NaCl, respectively in each of the samples.Concentrations of the solutions were 2.4 mol/L, except for K₂SO₄ (Sample46), which was less than 2.4 molar due to solubility limitations. Awater quenched aggregate was provided as a control in Sample 43. Theaggregates were allowed to lab air dry at standard conditions for 27hours, at 73+/−3° F. and 50% relative humidity.

The efficacy of water retention of the aggregates is inversely indicatedby weight percentage of water loss as shown in FIG. 1. The anhydroussodium acetate (NaAc) of Example 11 reduced the water evaporation toabout 41% of that of plain water.

The same aggregates as in Samples 44-50 were re-immersed in water for 30minutes after being allowed to dry, which is the normal delivery timefor ready-mixed concrete. The solution treated aggregates of theseSamples 51-57 not only lost less water during drying as indicated inFIG. 1, but also re-absorbed more water when re-immersed for 30 minutes,as indicated in FIG. 2, which plots the unfilled water weight percentagerelative to the weight of the aggregates. Assuming the 25% weight gainby quenching with solution indicates full saturation of the lightweight,the graph displays the remaining capillary space in the lightweightafter being placed in the concrete mix prior to pump delivery.

The usual weight of lightweight coarse aggregate per cubic yard ofconcrete ranges from 750 to 900 pounds. If the sodium acetate treatedmaterial of Sample 47 were pumped at high pressure, it is estimated thatthe absorption of free water by the aggregates would be about 28-34pounds. If the water quenched material of Sample 43 were to be utilized,the potential absorption of free water by the aggregates would be about73-88 pounds.

Solution quenching or soaking lightweight aggregates, therefore, willprolong moisture condition during transport and storage. In addition,the air space in the pores of treated lightweight aggregates can be moreeasily and fully filled with water, reducing the quantity and rate ofwater emissions from the concrete in which they are contained.

Example 12

The purpose of the tests in Example 12 was to demonstrate that evenpartially filling the lightweight pores with various ionic solutesresulted in lower levels of water vapor emission in the low-densityconcrete products. The water-cement ratio was <0.45 in added water basedon saturated surface dried (SSD) aggregates. The water in thelightweight (not included in this calculation) was about 60 additionalpounds. The emissions were obtained from the same concrete mix usingdiffering solute-treated lightweight coarse aggregates. All aggregateswere boiled and cooled in solution, or in the case of the tap water,were soaked for 7 days. The concretes were flushed to remove externaldeposits and then cast in 6×6×2.5 inch rectangular pans, sealed for 3days to cure and then weighed at intervals to measure moisture vaporemissions until they reached the same level of moisture content of 7.8%of dry weight. Vapor loss measurements were determined based on thechanges in weight of the samples and is shown in FIG. 3. The temperaturewas 73° F.+/−3 and about 50% relative humidity.

As shown in FIG. 3, water and four salt solutions were used to treat theaggregates: tap water (H₂O, Sample 51), sodium silicate 8 wt % aqueoussolution (NaSiO₃, Sample 52), 20 wt % aqueous solution of anhydroussodium acetate (NaAc, Sample 53), 20 wt % aqueous solution of potassiumsulfate (K₂SO₄, Sample 54), and 20 wt % aqueous solution of potassiumcarbonate (K₂CO₃, Sample 55). While the concrete made with NaAc treatedaggregates (Sample 53) has a water vapor emission of about 12 grams, theconcrete made with tap water treated aggregates (Sample 51) has a watervapor emission of about 30 grams.

Example 13

Certain vectors or chemicals that effect change in the concrete as aconsequence of their dissolution into the paste may be attached to thelightweight aggregate by allowing a short surface drying time and thenapplying the appropriate solution to the aggregate or leaving the soakor quench solution on the surface to evaporate and deposit its solute.

The purpose of the tests in Example 13 was to demonstrate the advantageof using the absorbent lightweight as a carrier or vector for materialsthat accelerate hydration of the cementitious medium thereby promotingdensification and hydration. FIG. 4 shows water vapor emission ofconcrete made from aggregates treated by tap water (Sample 56) and foursolutions (Samples 57-60), wherein aggregates were soaked in water(Sample 56) or boiled in aqueous solutions (Samples 57, 58, and 59) orpartially dried then dipped in an aqueous solution of 15% NaAc and 5%NaCl (Sample 60).

Vapor loss measurements are provided in FIG. 4 for concretes made fromboiled and soaked aggregates versus dipped aggregates. The measurementswere determined based on the changes in weight of the samples. Incontrast to Samples 51-55, aggregates were not flushed before beingblended in concrete mixtures.

The “NaAC/NaCl” dipped Sample 60 portrays concrete made with alightweight partially dried (1.8% internal moisture), immersed for 5seconds in the noted solution, allowed to surface dry, and placed in aconcrete mix proportioned the same as the other samples. The notedsolution is an aqueous solution with 15 wt % of sodium acetate and 5 wt% of sodium chloride.

As evident in FIG. 4, the aggregates that were dipped in the notedsolution can be made into a concrete with much lower water vaporemission rate than a concrete made with aggregates treated with wateronly, such that the rate approximates a concrete made from aggregatesboiled and soaked with the same salt solution.

Example 14

The purpose of the test in Example 14 was to demonstrate the effect ofthe direct addition of salt(s) rather than infusion of the aggregates,according to certain other embodiments of the invention.

One or more salts from any of Samples 43-60 are added directly toconcrete having either stone or lightweight aggregate in an amount in arange of about 5 pounds to about 60 pounds of salt (dry weight) percubic yard of concrete, or about 10 pounds to about 50 pounds, or about15 pounds to about 40 pounds per cubic yard of concrete (e.g., in theamounts listed above in Tables 5-7). The resulting concrete provides foradequate drying for application of adhesive or water impermeable coatingwithin 60 days or less.

FIG. 5 is a graph showing representative samples of lightweight concretethat have been tested and which illustrate the close correlation betweenthe water evaporation rate and the number of days required for theconcrete to reach 75% relative humidity. The X axis is the test numberin a sequence of results chosen at random out of 270 tests that wererun. The right vertical axis depicts the number of days required toreach 75% IRH on a test cylinder of concrete with an imbedded humidityprobe. The left vertical axis depicts the mass of water vapor thatescaped from a sample in an evaporative pan made from the same batch.

The data in FIG. 5 illustrates the dichotomy that a higher moisture lossstrongly correlates with a prolonged time to reach a state of 75% IRH.This is the very opposite of standard concrete in which high moistureloss would normally indicate higher drying rate and faster time to reach75% IRH. Since the water contents are the same in each companion sample,it would indicate that the internal pore structure appears to be takingup the available water as it forms, thus inhibiting evaporation as thesmall pores form and reduce internal humidity. As set forth in theresearch described below, the smaller pores contain water that islargely non-evaporable, thus the Kelvin equation reflects this with thepore size controlling the IRH of a system.

Yang, et al., “Self-desiccation mechanism of high-performance concrete,”Research Lab of Materials Engineering, College of Materials Science andEngineering, Tongji University, Shanghai 200433, China, received Jul. 9,2003, revision accepted Mar. 15, 2004, explained the phenomenon asfollows.

Abstract: Investigations on the effects of W/C ratio and silica fume onthe autogenous shrinkage and internal relative humidity of highperformance concrete (HPC), and analysis of the self-desiccationmechanisms of HPC showed that the autogenous shrinkage and internalrelative humidity of HPC increases and decreases with the reduction ofW/C respectively; and that these phenomena were amplified by theaddition of silica fume. Theoretical analyses indicated that thereduction of IRH in HPC was not due to shortage of water, but due to thefact that the evaporable water in HPC was not evaporated freely. Thereduction of internal relative humidity or the so-calledself-desiccation of HPC was chiefly caused by the increase in moleconcentration of soluble ions in HPC and the reduction of pore size orthe increase in the fraction of micro-pore water in the total evaporablewater (Tr/Tte ratio).

Autogenous shrinkage is a term that describes the change in volume ofthe concrete that is driven by internal forces as opposed to externalforces such as evaporation or temperature change. Yang, et al. continuein this vein and conclude that “Theoretical analyses and calculationshowed that the reduction of IRH in HPC is not due to shortage of water,but due to the fact that the evaporable water in HPC is not evaporatedfreely. The main reasons behind the reduction of internal relativehumidity or so-called self-desiccation are the increase in moleconcentration of soluble ions and the reduction of pore size or theincrease in the fraction of micro-pore water in the total evaporablewater.” This analysis was based on the availability of ions from thecement assuming soluble alkali cement content of 0.6% as sodium oxide orhydrated, 6 pounds of sodium hydroxide (NaOH) in a mix similar to theHPC mix set forth in Table II above.

Example 15

The purpose of the test in Example 15 was to illustrate the beneficialeffect on drying time by incorporating hydrophilic salts directly intoconcrete during the mixing process. Samples 61-64 demonstrate shortdrying times using hydrophilic salts in lightweight concrete. Samples65-68 demonstrate short drying times using hydrophilic salts in normalweight concrete. FIG. 6 shows days to 75% humidity for the compositionsof Samples 61-64 having about 1.1 wt % NaNO₂, about 0.3 wt % sodiumthiosulfate hydrate, 0.8 wt % sodium thiosulfate hydrate, and about 1.25wt % sodium thiosulfate hydrate, respectively. FIG. 7 shows days to 75%humidity for the compositions of Samples 65-68 having about 0.28 wt %sodium thiosulfate hydrate and about 0.09 wt % sodium thiocyanate, about0.28 wt % sodium thiosulfate hydrate, about 0.55 wt % sodium thiosulfatehydrate and about 0.09 wt % sodium thiocyanate, and about 0.55 wt %sodium thiosulfate hydrate, respectively. (Note: “TS”=SodiumThiosulfate, Na₂S₂O₃.5H₂O, M.W. 248; “TC”=Sodium Thiocyanate, NaSCN, M.W80).

Concrete compositions were made according to Samples 61-68 having thefollowing compositions and data as set forth in Table 24 below.

TABLE 24 Sample Component (lbs) 61 62 63 64 65 66 67 68 Cement 400 400400 400 300 300 300 300 Slag (GGBFS) 400 400 400 400 300 300 300 300ASTM c-33 Sand 1400 1400 1400 1400 1300 1300 1300 1300 Lightweight 17%950 950 950 950 0 0 0 0 water by dry wt. Pea Gravel 0 0 0 0 1700 17001700 1700 Water 325 325 325 325 325 325 325 325 Na₂S₂O₃•5H₂O 0 10 25 4010 10 20 20 NaNO₂ 35 0 0 0 0 0 0 0 NaSCN 0 0 0 0 3.2 0 3.2 0 Other DataTime to 4:10 4:00 3:45 3:00 3:30 3:45 3:30 3:15 Temperature Rise Waterreducer: 2.9 2.9 2.9 2.9 2.9 2.9 2.9 2.9 oz/100 lbs

It has been found that additions of sodium or potassium thiosulfate(known as “hypo” in photography) impart significant acceleration ofhardening to concrete mixtures. This chemical, or mixtures containing itas a partial component, are effective in increasing the rate of internalhumidity reduction. Complementary to this, limited amounts of sodium orpotassium thiocyanate may be used as well. The thiocyanate ion inconcentrations greater than 1% by weight of cement is known create acondition that can be corrosive to reinforcement and is thereforelimited for durability reasons. If the concrete is to be dry in service,larger amounts may be used (assuming prior investigation of galvanicactivity potential).

Example 16

The purpose of the test in Example 16 was to illustrate the beneficialeffect on relative humidity over time by using sodium nitritesubstantially free of a silica fume in a cementitious mix according toan embodiment of the invention and sodium nitrate and a silica fume in acementitious mix according to another embodiment of the invention.Sample 69 is a cementitious mix having about 30 lb/yd³ of sodium nitritebut substantially free of silica fume. Sample 70 is a cementitious mixhaving about 20 lb/yd³ of sodium nitrite and about 15% by weight of thecementitious mix. FIG. 8 is a graphical representation showing therelative humidity over time for these two exemplary embodiments ofcementitious mixes of the invention. As shown in FIG. 8, Sample 70having silica fume and 20 lb/yd³ of sodium nitrite has about a 4%reduction in average relative humidity in comparison to Sample 69 having30 lb/yd³ of sodium nitrite but being substantially free of silica fume.Indeed, as further shown in FIG. 8, the relative humidity of thecementitious mix having both the sodium nitrite and silica fume beginsto experience relative humidities that are lower than that of Sample 69after about 22 days of drying.

Example 17

The purpose of the test in Example 17 was to illustrate the beneficialeffect on relative humidity over time by using increasing concentrationsof sodium nitrite in a cementitious mix according to an embodiment ofthe invention. Sample 71 has no sodium nitrite, while samples 72, 73,74, and 75 have 10 lb/yd³, 20 lb/yd³, 30 lb/yd³, and 40 lb/yd³ of sodiumnitrite, respectively. As shown in FIG. 9, which is a chart illustratingthe relative humidity over time for cementitious compositions havingvarious concentration of sodium nitrite according to certain embodimentsof the invention, the cements having greater amounts of sodiumnitrite—i.e., on the order of 30 lb/yd³ to even 40 lb/yd³—exhibit thegreatest relative reductions in relative humidity over the course ofdrying the concrete. As further shown in FIG. 9, the use of these higherconcentrations of sodium nitrite lead to relative humidities that areabout 20% less than the relative humidity of the concrete substantiallyfree of sodium nitrite after about 25 days of drying time. According tothese examples, the use of on the order of 40 lb/yd³ of sodium nitriteresults in a reduction in relative humidity of about 9% in comparison tothe relative humidity of a concrete having about 10 lb/yd³ of sodiumnitrite.

Example 18

The purpose of the test in Example 18 was to illustrate the beneficialeffect on relative humidity over time by using increasing concentrationsof sodium nitrite in a cementitious mix according to another embodimentof the invention having a different kind of cement than that used inExample 17. Sample 76 has no sodium nitrite, while samples 77, 78, 79,and 80 have 10 lb/yd³, 20 lb/yd³, 30 lb/yd³, and 40 lb/yd³ of sodiumnitrite, respectively. As shown in FIG. 9, which is a chart illustratingthe relative humidity over time for cementitious compositions havingvarious concentration of sodium nitrite according to certain embodimentsof the invention, the cements having greater amounts of sodiumnitrite—i.e., on the order of 30 lb/yd³ to even 40 lb/yd³—exhibit thegreatest relative reductions in relative humidity over the course ofdrying the concrete. As further shown in FIG. 10, the use of thesehigher concentrations of sodium nitrite lead to relative humidities thatare about 20% less than the relative humidity of the concretesubstantially free of sodium nitrite after about 25 days of drying time.Furthermore, the use of on the order of 40 lb/yd³ of sodium nitriteresults in a reduction in relative humidity of about 6% in comparison tothe relative humidity of a concrete having about one-half of thatconcentration of sodium nitrite. Examples 17 and 18 show the unexpectedresults that can be achieved based upon the mere differences in types ofcement that are used.

Example 19

The purpose of the test in Example 19 was to illustrate the extent ofreductions in relative humidity over time by using increasingconcentrations of sodium nitrite in a cementitious mix according to yetanother embodiment of the invention. Sample 81 has no sodium nitrite,while samples 82, 83, and 84 have 20 lb/yd³, 30 lb/yd³, and 40 lb/yd³ ofsodium nitrite, respectively. As shown in FIG. 11, which is a graphillustrating the internal relative humidity over time for thecementitious compositions of samples 81-84. In the exemplary examples ofFIG. 11, the cementitious composition of Sample 84 having about 40 pcyor 1 lb/yd³ of sodium nitrite generally provides the lowest internalrelative humidity for these concretes.

Comparative Study

A comparative study was performed comparing the difference in internalrelative humidity achieved by various cementitious compositions. Thecementititous compositions of Test Runs 3, 5-7, 9-13, and 15-16 areexamples of embodiments employing alkali metal salts in accordance withthe disclosed invention. Test Runs 1A, 1B, 3, 4, 8 and 14 arecomparative examples of cementitious compositions that do not employalkali metal salts and do not perform in accordance with the disclosedinvention. Test Runs 8 and 14 are further show that employing analkaline earth metal salt (calcium nitrate) is not significantly betterthan using no salt relative to achieving a desired low IRH.

Test Runs 1 to 3

Test Runs 1 and 2 were prepared according to Example 1 of EP 1903014(Chanvillard et al.), with Test Run 1B being a repeat of Test Run 1A.Test Run 3 was prepared in an identical manner to Test Runs 1 and 2,except that Test 3 included a water vapor attenuation agent, i.e.,sodium nitrite. The cementitious compositions were formed into 4 inchmortar cylinders. The cementitious compositions for Test Runs 1 to 3 areset forth in Table 25.

TABLE 25 Test Run Component and Amount 1A 1B 2 3 Cement - HansonCupertino Type II/V (g) 500 500 500 500 Slag - Lehigh Nippon Grade 120(g) 215 215 215 215 Expansive Agent - Calcium Oxide (g) 42 42 — 42 WaterVapor Attenuation Agent - Sodium — — — 22 Nitrite (g) Fine Aggregate -Vulcan Pleasanton Top 1434 1434 1434 1434 Sand (g) Shrinkage ReducingAgent - MasterLIFE 3.3 3.3 3.3 3.3 20 (ml) Glenium 7500 superplasticizer(ml) 2.1 2.1 2.1 2.1 Water (g) 290 290 280 293 Water-to-CementitiousBinder Ratio 0.38 0.38 0.39 0.38 (w/cm)

The internal relative humidities for Test Runs 1 to 3 were periodicallymeasured using Vaisala HMP40s relative humidity sensors and are setforth in Table 26. FIG. 12 is a bar graph comparing the 19-day internalrelative humidity for Test Runs 1 to 3. FIG. 13 is a line graphcomparing the internal relative humidity for Test Runs 1 to 3 for allsampled days.

TABLE 26 Internal Relative Humidity Test Run (Day and %) 1A 1B 2 3 Day10 93.7 93.6 91.9 83 Day 11 96.0 97.7 94.6 86 Day 12 96.3 96.2 94.7 85.8Day 14 95.5 95.8 94 84.1 Day 19 94.8 95.2 94.3 82.6 Day 21 94.6 94.493.4 82.3 Day 25 93.6 93.2 92.7 81 Day 28 92.9 92.7 92.2 80.1 Day 3292.7 91.3 91.9 79.1 Day 35 92.4 90.6 91.3 78.4 Day 38 91.7 90.1 90.578.1 Day 41 91 90.6 90.3 77.8 Day 45 90.5 89 90.3 77.1 Day 47 90.4 87.989.7 76.2

As shown in Table 31 and FIGS. 12 and 13, the internal relative humidityvalues for Test Run 3 at each day were significantly lower than for eachof Test Runs 1 and 2. Moreover, the highest internal relative humidityvalue for Test Run 3 occurred at Day 11 and was significantly lower thanthe lowest internal relative humidity values for Test Runs 1 and 2,which occurred at Day 47. This data indicate that the addition of sodiumnitrite caused a dramatic reduction in the internal relative humidity ofthe cementitious composition compared to the same or similarcompositions made according to Chanvillard.

Test Runs 4 to 7

Test Run 4 was prepared in a manner consistent with Example 1 ofChanvillard but included less cement and more slag. Test Runs 5 to 7were prepared in similar fashion, except that a water vapor attenuationagent—sodium nitrite—was added to the cementitious compositions and theamounts of other components were altered to determine if and how suchalterations would affect the internal relative humidity. Further, theamount of the water vapor attenuation agent (sodium nitrite) in TestRuns 5 to 7 was greater than in Test Run 3, above. The cementitiouscompositions for Test Runs 4 to 7 are set forth in Table 27.

TABLE 27 Test Run Component and Amount 4 5 6 7 Cement - Hanson CupertinoType II/V (g) 400 400 400 400 Slag - Lehigh Nippon Grade 120 (g) 400 400400 400 Expansive Agent - Calcium Oxide (g) — — 44 — Water VaporAttenuation Agent - Sodium — 40 40 40 Nitrite (g) Fine Aggregate -Vulcan Pleasanton Top 1400 1400 1400 1400 Sand (g) Shrinkage ReducingAgent - MasterLIFE 8.3 8.3 8.3 — 20 (ml) Glenium 7500 superplasticizer(ml) 2.4 2.3 2.3 2.6 Water (g) 267 267 282 267 Water-to-CementitiousBinder Ratio 0.33 0.33 0.33 0.33 (w/cm)

The internal relative humidities for Test Runs 4 to 7 were periodicallymeasured using Vaisala HMP40s relative humidity sensors and are setforth in Table 28. FIG. 14 is a bar graph comparing the 19-day internalrelative humidity for Test Runs 4 to 7. FIG. 15 is a line graphcomparing the internal relative humidity for Test Runs 4 to 7 for allsampled days.

TABLE 28 Internal Relative Humidity Test Run (Day and %) 4 5 6 7 Day 1091 73.5 73 72.8 Day 11 92.8 76 75 74.7 Day 12 93.7 76.8 75.8 75.7 Day 1492.7 73.7 72.7 73 Day 19 91.8 73 71.9 71.5 Day 21 91.8 72.4 71.4 71.3Day 25 90.4 70.2 70.6 70.1 Day 28 90.1 69.9 70 69.5 Day 32 89.6 70.469.7 69.2 Day 35 89.1 69.6 68.9 69 Day 38 88.6 69.4 69.2 68.5 Day 4189.1 69.9 69.9 68.8 Day 45 88.1 98.7 68.8 68.5 Day 47 87.4 68.8 68.367.8

As shown in Table 3 and FIGS. 14 and 15, the internal relative humidityvalues for Test Runs 5 to 7 were significantly lower than that of TestRun 4. Moreover, the highest internal relative humidity values for TestRuns 5 to 7 occurred at Day 12 and were significantly lower than thelowest internal relative humidity value for Test Run 4, which occurredat Day 47 This data indicate that the addition of sodium nitrite causeda dramatic reduction in the internal relative humidity of thecementitious composition compared to the same or similar compositions.

FIG. 16 is a bar graph comparing the 10-day internal relative humidityfor Test Runs 1 to 7, which graphically illustrates the dramaticallylower internal relative humidity values for Test Runs 3 and 5 to 7,which contained sodium nitrite, compared to Test Runs 1A, 1B, 2 and 4,which contained no sodium nitrite. FIG. 16 also illustrates the furtherreduction in internal relative humidity values for Test Runs 5 to 7 as aresult of including a higher quantity of sodium nitrite compared to TestRun 3.

This data indicate that addition of sodium nitrite caused a substantialreduction in internal relative humidity and that including or notincluding an expansive agent and/or a shrinkage reducing agent ofChanvillard had no significant effect on internal relative humidity.This data further demonstrate that using an increased amount of sodiumnitrite further reduced the internal relative humidity compared to usinga lower amount, thereby showing a clear discernable trend covering arange of alkali metal salt concentrations. We qualify this statement bynoting that reducing the w/cm from 0.38 (Run 1) to 0.33 (Run 4) and/oraltering the quantities of cement and slag from 500 g and 210 g (Runs 1to 3) to 400 g and 400 g (Runs 4 to 7), respectively, apparently reducedthe 14-day internal relative humidity from 95.5 (Run 1) to 92.7 (Run 4).However, in the absence of including the alkali metal salt, suchmeasures did not cause the cementitious compositions to achieve an IRHof 75% in 50 days or less.

Test Runs 8 to 13

The cementitious compositions for Test Runs 8 to 13 are set forth inTable 29 and included one of various alkali metal or alkaline earthmetal salts.

TABLE 29 Test Run Component and Amount 8 9 10 11 12 13 Cement - HansonCupertino 400 400 400 400 400 400 II/V (g) Slag - Lehigh Muroran (g) 400400 400 400 400 400 Fine Aggregate - Hanson 1300 1300 1300 1300 13001300 Sechelt (g) Glenium 7500 (ml) 2.3 2.9 3.1 2.9 2.9 2.8 CalciumNitrate (g) 47.6 — — — — — Sodium Nitrite (g) — 20 — — — — LithiumNitrate (g) — — 20 — — — Sodium Bromide (g) — — — 34.5 — — SodiumChloride (g) — — — — 16.9 — Potassium Chloride (g) — — — — — 21.6 Water,As Batched (g) 270 270 270 270 270 270

Test Runs 8 to 13 compared the effect of various salts on internalrelative humidity (IRH) using a standard cementitious composition. TheIRH values for Test Runs 8 to 13 were tested in a manner similar to TestRuns 1 to 7 and are set forth in the line graph of FIG. 17. As shown bythe test data in FIG. 17, the alkali metal salts—sodium nitrite, lithiumnitrate, sodium bromide, sodium chloride, and potassium chloride—werefar superior to calcium nitrate in reducing IRH. There was littledifference between lithium nitrate and sodium nitrite, which indicatesthat lithium and sodium salts behave similarly, as do nitrate andnitrite salts. The alkali metal halide salts all behaved about the sameregardless of the alkali metal cation or halide anion. However, calciumnitrate substantially underperformed every alkali metal salt. Alkalimetal salts were therefore found to be unexpectedly superior to calciumsalts in reducing IRH of concrete.

Test Runs 14 to 16

The cementitious compositions for Test Runs 14 to 16 are set forth inTable 30 and included either no salt, calcium formate, or sodiumformate.

TABLE 30 Test Run Component and Amount 14 15 16 Cement - HansonCupertino II/V (g) 800 800 800 Fine Aggregate - Hanson Sechelt (g) 14501450 1450 Glenium 7500 (ml) 2.6 2.9 2.9 Calcium Formate (g) — 20 —Sodium Formate (g) — — 20 Water, As Batched (g) 270 270 270

Test Runs 14 to 16 compared the effect on internal relative humidity(IRH) of using either no additive, calcium formate, or sodium formate ina standard cementitious composition. The IRH values for Test Runs 14 to16 were tested in a manner similar to Test Runs 1 to 7 and are set forthin the line graph of FIG. 18. As clearly shown, sodium formate was farsuperior to calcium formate in reducing internal relative humidity ofthe hardened concrete. In addition, using calcium formate was not muchbetter than using no additive at all. This further shows the unexpectedsuperiority of using alkali metal salts to reduce IRH and also theunexpected lack of benefit of using calcium formate in place of using noadditive.

All publications mentioned herein, including patents, patentapplications, and journal articles are incorporated herein by referencein their entireties including the references cited therein, which arealso incorporated herein by reference. The publications discussed hereinare provided solely for their disclosure prior to the filing date of thepresent application. Nothing herein is to be construed as an admissionthat the present invention is not entitled to antedate such publicationby virtue of prior invention. Neither should the citation of documentsherein be construed as an admission that the cited documents areconsidered material to the patentability of the claims of the variousembodiments of the invention. Further, the dates of publication providedmay be different from the actual publication dates which may need to beindependently confirmed.

Many modifications and other embodiments of the invention set forthherein will come to mind to one skilled in the art to which thisinvention pertains having the benefit of the teachings presented in thedescriptions herein and the associated drawings. For example, thoughvarious methods are disclosed herein, one skilled in the art willappreciate that various other methods now know or conceived in the artwill be applied to a subject in conjunction with the methods oftreatments or therapies disclosed herein. Therefore, it is to beunderstood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.

1. A cementitious composition comprising: a hydraulic cement; anaggregate; one or more water soluble alkali metal salts; and water,wherein the hydraulic cement, aggregate, one or more water solublealkali metal salts, water, and optional components are selected andproportioned so that the cementitious composition has a water tocementitious binder ratio (w/cm) in a range of 0.2 to 0.7 and produceshardened concrete that achieves an internal relative humidity (IRH) of80% or less in 50 days or less when evaluated in accordance with ASTM F2170.
 2. The cementitious composition of claim 1, wherein thecementitious composition produces hardened concrete that achieves aninternal relative humidity (IRH) of 75% or less in 50 days or less whenevaluated in accordance with ASTM F
 2170. 3. The cementitiouscomposition of claim 2, wherein the cementitious composition produceshardened concrete that achieves an internal relative humidity (IRH) of75% or less in less than about 45 days, 40 days, 35 days, 30 days, 28days, 25 days, 20 days, 15 days, or 10 days when evaluated in accordancewith ASTM F
 2170. 4. The cementitious composition of claim 1, whereinthe hydraulic cement, aggregate, one or more water soluble alkali metalsalts, water, and optional components are selected and proportioned sothat the cementitious composition produces hardened concrete in 50 daysor less containing a number of moles of remaining free water and anumber of moles of dissolved ions according to Equation (I):Moles Free Water÷(Moles Free Water+Moles Dissolved Ions)≦0.80   Equation(I).
 5. The cementitious composition of claim 4, wherein:Moles Free Water÷(Moles Free Water+Moles Dissolved Ions)≦75.
 6. Thecementitious composition of claim 1, wherein the one or more watersoluble alkali metal salts are selected from the group consisting ofacetates, formates, sulfates, thiosulfates, nitrates, nitrites,bromides, chlorides, and thiocyanates of one or more alkali metals. 7.The cementitious composition of claim 6, wherein the one or more watersoluble alkali metal salts are selected from the group consisting ofsodium formate, sodium acetate, sodium nitrate, sodium nitrite, sodiumsulfate, potassium sulfate, sodium chloride, sodium silicate, sodiumthiosulfate hydrate, sodium thiocyanate, and combinations thereof
 8. Thecementitious composition of claim 6, wherein the one or more watersoluble alkali metal salts comprise sodium nitrite.
 9. The cementitiouscomposition according to claim 6, wherein the one or more water solublealkali metal salts comprise sodium formate.
 10. The cementitiouscomposition according to claim 6, wherein the one or more water solublealkali metal salts comprise sodium acetate.
 11. The cementitiouscomposition according to claim 1, wherein the one or more water solublealkali metal salts comprises sodium nitrite having a concentration in arange of about 5 pcy to about 60 pcy.
 12. The cementitious compositionaccording to claim 12, wherein the sodium nitrite has a concentration ina range of about 10 pcy to about 50 pcy.
 13. The cementitiouscomposition according to claim 12, wherein the sodium nitrite has aconcentration in a range of about 20 pcy to about 40 pcy.
 14. Thecementitious composition according to claim 1, wherein the one or morewater soluble alkali metal salts comprises an alkali metal salt having aconcentration in a range of about 5 (MW/IPM) pcy to about 60 (MW/IPM)pcy, where MW=molecular weight and IPM=ions per mole for the alkalimetal salt.
 15. The cementitious composition according to claim 14,wherein the alkali metal salt has a concentration in a range of about 10(MW/IPM) pcy to about 50 (MW/IPM) pcy.
 16. The cementitious compositionaccording to claim 14, wherein the alkali metal salt has a concentrationin a range of about 20 (MW/IPM) pcy to about 40 (MW/IPM) pcy.
 17. Thecementitious composition of claim 1, wherein the aggregate comprises aporous lightweight aggregate so that the cementitious composition yieldslightweight concrete.
 18. The cementitious composition of claim 1,further comprising at least one of a reactive pozzolan orsuperplasticizer.
 19. A concrete composition comprising the mixtureproducts of: a hydraulic cement; an aggregate; one or more water solublealkali metal salts; and water, wherein the hydraulic cement, aggregate,one or more water soluble alkali metal salts, water, and optionalcomponents are selected and proportioned so that the concretecomposition, when freshly prepared, has a water to cementitious binderratio (w/cm) in a range of 0.2 to 0.7 and, after hardening, achieves aninternal relative humidity (IRH) of 80% or less in 50 days or less whenevaluated in accordance with ASTM F
 2170. 20. The concrete compositionof claim 19, wherein the aggregate comprises a porous lightweightaggregate so that the concrete composition is lightweight concrete. 21.A method of manufacturing a hardened concrete, comprising: preparing afresh concrete mixture by blending together hydraulic cement, aggregate,a water soluble alkali metal salt, and water, the water including bothwater of hydration and excess water; allowing the water of hydration toreact with the hydraulic cement to form hydrated cement paste havingpores and capillaries; the water soluble alkali metal salt enhancingretention of the excess water by pores and capillaries of the hydratedcement paste and inhibiting diffusion of water through the concrete to asurface of the hardened concrete; and the hardened concrete more quicklyachieving a desired internal relative humidity (IRH) and surface drynesscompared to hardened concrete made in the absence of the alkali metalsalt.
 22. The method of claim 21, wherein at least a portion the alkalimetal salt is added when preparing the fresh concrete mixture.
 23. Themethod of claim 21, wherein aggregate comprises a lightweight porousaggregate, the method further comprising infusing at least a portion ofthe alkali metal salt into the lightweight porous aggregate using anaqueous salt solution prior to preparing the fresh concrete mixture. 24.The cementitious composition of claim 23, the alkali metal salt having aconcentration in a range of about 8% to about 20% by weight of theaqueous salt solution.
 25. The method of claim 21, wherein the alkalimetal salt causes the concrete to achieve an internal relative humidity(IRH) of 75% or less in 50 days or less.
 26. The method of claim 21,wherein the alkali metal salt causes the hardened concrete to have lessautogenous and/or drying shrinkage compared to concrete substantiallyfree of the alkali metal salt.
 27. The method of claim 21, wherein thealkali metal salt causes the hardened concrete to achieve the desiredinternal relative humidity while having a higher water-to-cementitiousbinder ratio (w/cm) and/or with less superplasticizer compared to ahardened concrete made without the alkali metal salt.
 28. The method asin claim 21, wherein the aggregate comprises a porous aggregate andwherein the alkali metal salt reduces inflow and outflow of water frompores and capillaries of the porous aggregate compared to a hardenedconcrete made without the alkali metal salt.
 29. The method as in claim21, wherein the aggregate comprises a porous lightweight aggregate andwherein the alkali metal salt improves workability and pumpability ofthe fresh concrete mixture compared to a fresh concrete mixture madewithout the alkali metal salt while also causing the hardened concreteto achieve the desired internal relative humidity (IRH) at the same orhigher w/cm compared to a hardened concrete mixture made without thealkali metal salt.